NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

Tan SL, editor. Hepatitis C Viruses: Genomes and Molecular Biology. Norfolk (UK): Horizon Bioscience; 2006.

Cover of Hepatitis C Viruses

Hepatitis C Viruses: Genomes and Molecular Biology.

Show details

Chapter 1HCV Genome and Life Cycle

and .

Abstract

Hepatitis C virus (HCV) infection afflicts more than 170 million people worldwide, with the great majority of patients with acute hepatitis C developing chronic HCV infection. It can ultimately result in liver cirrhosis, hepatic failure or hepatocellular carcinoma, which are responsible for hundreds of thousands of deaths each year. Despite the discovery of HCV over 15 years ago, our knowledge of the HCV lifecycle has been limited by our inability to grow the virus in cell culture, as well as by the lack of small-animal models of HCV infection. Nevertheless, data accumulated through the use of multiple in vitro and in vivo study systems have provided a general picture of the biology of HCV, although sometimes with contradictory results. Herein, we summarize our current understanding of the HCV genome and how its structure and encoded gene products, in a complex interplay with host cell factors, might orchestrate a productive viral lifecycle while evading the scrutiny of the host immune system. The recently developed robust in vitro HCV infection systems should help fill in some of the gaps in understanding the HCV lifecycle in the next few years.

HCV Genome Organization and Function

The Flaviviridae family is divided into three genera: flavivirus, pestivirus, and hepacivirus. Flaviviruses include yellow fever virus, dengue fever virus, Japanese encephalitis virus, and Tick-borne encephalitis virus. Pestiviruses include bovine viral diarrhea virus, classical swine fever virus and Border disease virus. HCV, with at least 6 genotypes and numerous subtypes, is a member of the hepacivirus genus, which includes tamarin virus and GB virus B (GBV-B) and is closely related to human virus GB virus C (GBV-C) (Lindenbach and Rice, 2001).

The members of the Flaviviridae family share a number of basic structural and virological characteristics. They are all enveloped in a lipid bilayer in which two or more envelope proteins (E) are anchored. The envelope surrounds the nucleocapsid, which is composed of multiple copies of a small basic protein (core or C), and contains the RNA genome. The Flaviviridae genome is a positive-strand RNA molecule ranging in size from 9.6 to 12.3 thousand nucleotides (nt), with an open reading frame (ORF) encoding a polyprotein of 3000 amino acids (aa) or more.

The structural proteins are encoded by the N-terminal part of the ORF, whereas the remaining portion of the ORF codes for the nonstructural proteins (Fig. 1). Sequence motif-conserved RNA protease-helicase and RNA-dependant RNA polymerase (RdRp) are found at similar locations in the polyproteins of all of the Flaviviridae (Miller and Purcell, 1990). In addition, all Flaviviridae share similar polyprotein hydropathic profile, with flaviviruses and hepaciviruses being closer to each other than to pestiviruses (Choo et al., 1991). The ORF is flanked in 5′ and 3′ by untranslated regions (UTR) of 95–555 and 114–624 nt in length, respectively, which play an important role in polyprotein translation and RNA replication (Fig. 1) (Thurner et al., 2004).

Fig. 1. Organization of Flaviviridae genomes.

Fig. 1

Organization of Flaviviridae genomes. The figure shows, from top to bottom, the genomes of HCV (hepacivirus), pestivirus, and yellow fever virus (flavivirus). NS: non structural.

Flaviviridae bind to one or more cellular receptors organized as a receptor complex and appear to trigger receptor-mediated endocytosis. Fusion of the virion envelope with cellular membranes delivers the nucleocapsid to the cytoplasm. After decapsidation, translation of the viral genome occurs in the cytoplasm, leading to the production of a precursor polyprotein, which is then cleaved by both cellular and viral proteases into structural and nonstructural proteins. Replication of the viral genome is carried out by the viral replication complex which is associated with cellular membranes and resistant to actinomycin D. Viral replication occurs in the cytoplasm via the synthesis of full-length negative-strand RNA intermediates. Progeny virions are assembled from cytoplasmic vesicles formed by budding through intracellular membranes. Finally, mature virions are released into the extracellular milieu by exocytosis.

Despite the above-mentioned similarities with the members of other Flaviviridae genera, HCV does exhibit a number of virological, epidemiological as well as pathophysiological differences. Flavivirus translation is cap-dependent, i.e. mediated by a type I cap structure located in the 5′ UTR (m7GpppAmp), followed by the conserved AG sequence and a relatively short stretch upstream of the polyprotein coding region (Brinton and Dispoto, 1988). In contrast, the HCV 5′ UTR is not capped and, like that of pestiviruses and GB viruses, folds into a complex secondary RNA structure forming, together with a portion of the core-coding domain, an internal ribosome entry site (IRES) that mediates direct binding of ribosomal subunits and cellular factors and subsequent translation (see Chapter 2). Whereas the flavivirus 3′ UTR is highly structured, the HCV 3′ UTR is relatively short, less structured and contains a poly-uridyl tract that varies in length.

HCV has a narrow host specificity and tissue tropism. HCV is transmitted exclusively through direct blood-to-blood contacts between humans. Flaviviruses are principally vectored by mosquitoes or ticks and can infect a broad range of vertebrate animals, with humans being a dead-end host that does not participate in the perpetuation of virus transmission. No known pestivirus can infect humans and no known insect vector has been identified. Infections caused by flaviviruses are acute-limited in vertebrate animals, whereas HCV has a high chronicity rate in humans (50%–80%, depending on the age at infection). Strong and adapted humoral and cellular immune responses have been shown to be involved in flavivirus and pestivirus infection recovery and protection. However, HCV infection induces an immune response that fails to prevent chronicity in most cases and does not confer protection against reinfection with homologous and heterologous strains in the chimpanzee model (Farci et al., 1997).

HCV Genome Structure and Organization

The structural organization of HCV genome is schematically depicted in Fig. 2.

Fig. 2. HCV genome organization (top) and polyprotein processing (bottom).

Fig. 2

HCV genome organization (top) and polyprotein processing (bottom). The 5′ UTR consists of four highly structured domains and contains the IRES. The 3′ UTR consists of stable stem-loop structures (more...)

5′ Untranslated Region

The HCV 5′ UTR contains 341 nt located upstream of the ORF translation initiation codon. It is the most conserved region of the genome (nt sequence identity is 60% with GBV-B and approximately 50% with pestiviruses (Choo et al., 1991; Han et al., 1991). The 5′ UTR contains four highly structured domains, numbered I to IV, containing numerous stem-loops and a pseudoknot (Brown et al., 1992; Wang et al., 1995). Domains II, III and IV together with the first 12 to 30 nt of the core-coding region constitute the IRES (Honda et al., 1996). Structural characterization by electron microscopy (EM) indicated that domains II, III and IV form distinct regions within the molecule, with a fl exible hinge between domains II and III (Beales et al., 2001). The HCV IRES has the capacity to form a stable pre-initiation complex by directly binding the 40S ribosomal subunit without the need of canonical translation initiation factors, an event that likely constitutes the fi rst step of HCV polyprotein translation.

Several reports suggested a tissue compartmentalization of IRES sequences (Laskus et al., 2000; Lerat et al., 2000; Nakajima et al., 1996; Shimizu et al., 1997). Infection of lymphoid cell lines with HCV genotype 1a H77 strain led to the selection of a quasispecies with nucleotide substitutions within the 5′ UTR relative to the inoculum that conferred a 2- to 2.5-fold increase in translation effi ciency in human lymphoid cell lines relative to monocyte, granulocyte or monocyte cell lines (Lerat et al., 2000). Furthermore, different translation effi ciencies of HCV quasispecies variants isolated from different cell types in the same patient were observed, suggesting cell type-specifi c IRES interactions with cellular factors may also modulate polyprotein translation (Forton et al., 2004; Laporte et al., 2000; Lerat et al., 2000).

3′ Untranlated Region

The 3′ UTR contains approximately 225 nt. It is organized in three regions including, from 5′ to 3′, a variable region of approximately 30–40 nt, a long poly(U)-poly(U/UC) tract, and a highly conserved 3′-terminal stretch of 98 nt (3′ X region) that includes three stem-loop structures SL1, SL2 and SL3 (Kolykhalov et al., 1996; Tanaka et al., 1995; Tanaka et al., 1996). The 3′ UTR interacts with the NS5B RdRp and with two of the four stable stem-loop structures located at the 3′ end of the NS5B-coding sequence (Cheng et al., 1999; Lee et al., 2004). The 3′ X region and the 52 upstream nt of the poly(U/C) tract were found to be essential for RNA replication, whereas the remaining sequence of the 3′ UTR appears to enhance viral replication (Friebe and Bartenschlager, 2002; Ito and Lai, 1997; Yi and Lemon, 2003a; Yi and Lemon, 2003b).

Characteristics and Functions of HCV Proteins

The HCV ORF contains 9024 to 9111 nt depending on the genotype. The ORF encodes at least 11 proteins, including 3 structural proteins (C or core, E1 and E2), a small protein, p7, whose function has not yet been definitively defined, 6 nonstructural (NS) proteins (NS2, NS3, NS4A, NS4B, NS5A and NS5B), and the so-called “F” protein which results from a frameshift in the core coding region (Fig. 2; Table 1). The characteristics and functions of HCV proteins are extensively described elsewhere in this book. Here, we provide a brief overview of the viral gene products and their roles in the HCV lifecycle.

Table 1. HCV proteins and their functions in the viral life cycle.

Table 1

HCV proteins and their functions in the viral life cycle. Adapted from Bartenschlager et al., 2004.

Structural Proteins

Core Protein

The HCV core protein is a highly basic, RNA-binding protein, which presumably forms the viral capsid (see Chapter 3). The HCV core protein is released as a 191 aa precursor of 23-kDa (P23). Although proteins of various sizes (17 to 23 kDa) were detectable, the 21-kDa core protein (P21) appeared to be the predominant form (Yasui et al., 1998). The core protein contains three distinct predicted domains : an N-terminal hydrophilic domain of 120 aa (domain D1), a C-terminal hydrophobic domain of about 50 aa (domain D2), and the last 20 or so aa that serve as a signal peptide for the downstream envelope protein E1 (Grakoui et al., 1993c; Harada et al., 1991; Santolini et al., 1994). Domain D1 contains numerous positive charges. It is principally involved in RNA binding and nuclear localization, as suggested by the presence of three predicted nuclear localization signals (NLS) (Chang et al., 1994; Suzuki et al., 1995; Suzuki et al., 2005). Domain D2 is responsible for core protein association with endoplasmic reticulum (ER) membranes, outer mitochondria membranes and lipid droplets (Schwer et al., 2004; Suzuki et al., 2005).

Both membrane-bound and membrane-free core proteins appear to exist as dimeric or multimeric forms. When expressed in various in vitro systems, including cell-free or mammalian, bacterial, insect or yeast cell culture models, the HCV core protein can form nucleocapsid-like particles (NLPs) (Baumert et al., 1998; Blanchard et al., 2002; Blanchard et al., 2003; Dash et al., 1997; Ezelle et al., 2002; Iacovacci et al., 1997; Klein et al., 2004; Mizuno et al., 1995; Pietschmann et al., 2002; Serafino et al., 1997; Shimizu et al., 1996). The region between aa 82 and 102 of hydrophilic domain D1 contains a tryptophan-rich sequence and has been suggested to allow the P21 core protein to interact with itself, a property not borne by the precursor P23 (Nolandt et al., 1997). On the other hand, the 75 N-terminal residues of the core protein appear sufficient for NLP assembly in a bacterial system (Majeau et al., 2004). Recently, two clusters of basic residues located in the 68 N-terminal nt were shown to play a critical role in capsid assembly in a cell-free system, whereas the region between aa 82 and 102 did not play a major role (Klein et al., 2005). The critical residues for capsid assembly remain to be precisely identified.

In addition to its role in viral capsid formation, the core protein has been suggested to directly interact with a number of cellular proteins and pathways that may be important in the viral lifecycle (McLauchlan, 2000). The HCV core protein has pro- and anti-apoptotic functions (Chou et al., 2005; Kountouras et al., 2003; Meyer et al., 2005), stimulates hepatocyte growth in Huh-7 cell line by transcriptional upregulation of growth-related genes (Fukutomi et al., 2005), and has been implicated in tissue injury and fibrosis progression (Nunez et al., 2004). The HCV core protein could also regulate the activity of cellular genes, including c-myc and c-fos, and alter the transcription of other viral promoters (Ray et al., 1995; Shih et al., 1993). It induces hepatocellular carcinoma when expressed in transgenic mice (Moriya et al., 1998; Moriya et al., 1997). It could also induce the formation of lipid droplets and may play a direct role in steatosis formation (Barba et al., 1997; Moriya et al., 1998; Moriya et al., 1997).

E1 and E2 Envelope Glycoproteins

The two envelope glycoproteins, E1 and E2, are essential components of the HCV virion envelope and necessary for viral entry and fusion (Bartosch et al., 2003a; Nielsen et al., 2004) (see Chapter 4). E1 and E2 have molecular weights of 33–35 and 70–72 kDa, respectively, and assemble as noncovalent heterodimers (Deleersnyder et al., 1997). E1 and E2 are type I transmembrane glycoproteins, with N-terminal ectodomains of 160 and 334 aa, respectively, and a short C-terminal transmembrane domain of approximately 30 aa. The E1 and E2 transmembrane domains are composed of two stretches of hydrophobic aa separated by a short polar region containing fully conserved charged residues. They have numerous functions, including membrane anchoring, ER localization and heterodimer assembly (Cocquerel et al., 1998; Cocquerel et al., 2000). The ectodomains of E1 and E2 contain numerous proline and cysteine residues, but intramolecular disulfide bonds have not been observed (Matsuura et al., 1994). E1 and E2 are highly glycosylated, containing up to 5 and 11 glycosylation sites, respectively. In addition, E2 contains hypervariable regions with aa sequences differing up to 80% between HCV genotypes and between subtypes of the same genotype (Weiner et al., 1991). Hypervariable region 1 (HVR1) contains 27 aa and is a major (but not the only) HCV neutralizing epitope (Farci et al., 1996; Zibert et al., 1997). Despite the HVR1 sequence variability, the physicochemical properties of the residues at each position and the overall conformation of HVR1 are highly conserved among all known HCV genotypes, suggesting an important role in the virus lifecycle (Penin et al., 2001).

E2 plays a crucial role in the early steps of infection. Viral attachment is thought to be initiated via E2 interaction with one or several components of the receptor complex (Flint and McKeating, 2000; Rosa et al., 1996). Because HVR1 is a basic region with positively charged residues located at specific sequence positions, it can theoretically interact with negatively charged molecules at the cell surface. This interaction could play a role in host cell recognition and attachment, as well as in cell or tissue compartmentalization (Barth et al., 2003; Bartosch et al., 2003b). In addition, it was recently shown that human serum facilitated infection of Huh7 cells by HCV pseudoparticles, apparently mediated through an interplay between serum high-density lipoproteins (HDL), HVR1 and the scavenger receptor B type I (SR-BI) (Bartosch et al., 2005; Voisset et al., 2005). Less is known about E1, but it is thought to be involved in intra-cytoplasmic virus-membrane fusion (Flint and McKeating, 2000; Rosa et al., 1996).

Frameshift Protein

The F (frameshift) protein or ARFP (alternate reading frame protein) is generated as a result of a −2/+1 ribosomal frameshift in the N-terminal core-encoding region of the HCV polyprotein. Antibodies to peptides from the F protein were detected in chronically infected patients, suggesting that the protein is produced during infection (Walewski et al., 2001). However, the exact translational mechanisms governing the frequency and yield of the F protein during the various phases of HCV infection are completely unknown. Thus, the role of F protein in the HCV lifecycle remains enigmatic but it was proposed to be involved in viral persistence (Baril and Brakier-Gingras, 2005).

Nonstructural Proteins

P7

p7 is a small, 63 aa polypeptide, that has been shown to be an integral membrane protein (Carrere-Kremer et al., 2002). It comprises two transmembrane domains organized in α-helices, connected by a cytoplasmic loop. p7 appears to be essential, because mutations or deletions in its cytoplasmic loop suppressed infectivity of intra-liver transfection of HCV cDNA in chimpanzees (Sakai et al., 2003). In vitro studies suggested that p7 belongs to the viroporin family and could act as a calcium ion channel (Gonzalez and Carrasco, 2003). However, these results remain to be confirmed in vivo.

NS2

NS2 is a non-glycosylated transmembrane protein of 21–23 kDa (see Chapter 5). It contains two internal signal sequences at aa positions 839–883 and 928–960, which are responsible for ER membrane association (Santolini et al., 1995; Yamaga and Ou, 2002). NS2, together with the amino-terminal domain of the NS3 protein, the NS2-3 protease, constitutes a zinc-dependent metalloprotease that cleaves the site between NS2 and NS3 (Grakoui et al., 1993b; Grakoui et al., 1993c; Hijikata et al., 1993). NS2 is a short-lived protein that looses its protease activity after self-cleavage from NS3 and is degraded by the proteasome in a phosphorylation-dependent manner by means of protein kinase casein kinase 2 (Franck et al., 2005). In addition to its protease activity, NS2 could interact with host cell proteins, such as the liverspecific pro-apoptotic cell death-inducing DFF45-like effector (CIDE-B), and affect reporter genes controlled by liver and non-liver-specific promoters and enhancers (Dumoulin et al., 2003; Erdtmann et al., 2003). However, the consequences of such interactions within the context of the HCV lifecyle are not clear.

NS3-NS4A

NS3 is a multi-functional viral protein containing a serine protease domain in its N-terminal third and a helicase/NTPase domain in its C-terminal two-thirds. NS4A is a cofactor of NS3 protease activity. NS3-4A also bears additional properties through its interaction with host cell pathways and proteins that may be important in the lifecycle and pathogenesis of infection (see Chapters 6 and 13). Not surprisingly, the NS3-NS4A protease is one of the most popular viral targets for anti-HCV therapeutics (Pawlotsky and McHutchison, 2004; Pawlotsky, 2006).

NS3-NS4A Protease

The NS3-NS4A protease is essential for the HCV lifecycle. It catalyzes HCV polyprotein cleavage at the NS3/NS4A, NS4A/NS4B, NS4B/NS5A and NS5A/NS5B junctions. The 3D structure of the NS3 serine protease domain complexed with NS4A has been determined (Kim et al., 1996; Love et al., 1996; Yan et al., 1998). The catalytic triad is formed by residues His 57, Asp 81 and Ser 139 (Bartenschlager et al., 1993; Grakoui et al., 1993a; Tomei et al., 1993). The central region of NS4A (aa 21–30) acts as a cofactor of NS3 serine protease activity, allowing its stabilization, localization at the ER membrane as well as cleaveage-dependent activation, particularly at the NS4B/NS5A junction (Bartenschlager et al., 1995; Lin et al., 1995; Tanji et al., 1995).

Recently, HCV NS3-NS4A was shown in vitro to antagonize the dsRNA-dependent interferon regulatory factor 3 (IRF-3) pathway, an important mediator of interferon induction in response to a viral infection (Foy et al., 2003). NS3-NS4A also appears to prevent dsRNA signaling via the toll-like receptor 3 upstream of IRF-3 (Li et al., 2005). One potential mechanism includes a blockade of the intracellular double-stranded RNA sensor protein (RIG-I) pathway by NS3-NS4A (Sumpter et al., 2005). Thus, HCV could utilize NS3-4A protease to circumvent the innate immune response at the early stages of infection. In addition, NS3 was also reported to induce malignant transformation of NIH3T3 cells (Sakamuro et al., 1995), suppress actinomycin D-induced apoptosis in murine cell lines (Fujita et al., 1996), and to be involved in hepatocarcinogenesis events (Borowski et al., 1996; Hassan et al., 2005), although the exact mechanisms are not clear.

NS3 Helicase-NTpase

The NS3 helicase-NTPase domain consisting of the 442 C-terminal aa of the NS3 protein is a member of the helicase superfamily-2 (see Chapter 7). Its three-dimentional structure has also been determined (Cho et al., 1998; Kim et al., 1998; Yao et al., 1997). The NS3 helicase-NTPase has several functions, including RNA-stimulated NTPase activity, RNA binding, and unwinding of RNA regions of extensive secondary structure by coupling unwinding and NTP hydrolysis (Gwack et al., 1997; Tai et al., 1996). During RNA replication, the NS3 helicase has been suggested to translocate along the nucleic acid substrate by changing protein conformation, utilizing the energy of NTP hydrolysis. A recent study proposed that the helicase directional movement step is fueled by single-stranded RNA binding energy, while NTP binding allows for a brief period of random movement that prepares the helicase for the next cycle (Levin et al., 2005). In addition, NS3 helicase activity appears to be modulated by the NS3 protease domain and the NS5B RdRp (Zhang et al., 2005).

NS4B

NS4B is an integral membrane protein of 261 aa with an ER or ER-derived membrane localization (Hugle et al., 2001; Lundin et al., 2003). NS4B is predicted to harbor at least four transmembrane domains and an N-terminal amphipathic helix that are responsible for membrane association (Elazar et al., 2004; Hugle et al., 2001; Lundin et al., 2003). One of the functions of NS4B is to serve as a membrane anchor for the replication complex (see Chapter 8) (Egger et al., 2002; Elazar et al., 2004; Gretton et al., 2005). Additional putative properties include inhibition of cellular syntheses (Florese et al., 2002; Kato et al., 2002), modulation of HCV NS5B RdRp activity (Piccininni et al., 2002), transformation of NIH3T3 cell lines (Park et al., 2000), and induction of interleukin 8 (Kadoya et al., 2005).

NS5A

NS5A is a 56–58 kDa phosphorylated zinc-metalloprotein that probably plays an important role in virus replication and regulation of cellular pathways (see Chapter 9). The N-terminal region of NS5A (aa 1–30) contains an amphipathic α-helix that is necessary and sufficient for membrane localization in perinuclear membranes as well as for assembly of the replication complex (Brass et al., 2002; Elazar et al., 2003; Penin et al., 2004a). Downstream of this motif, the NS5A protein was predicted to contain three domains, numbered I to III. Domain I, located at the N-terminus, contains an unconventional zinc-binding motif formed by four cysteine residues conserved among the hepacivirus and pestivirus genera (Tellinghuisen et al., 2004). HCV replicon RNA replication was inhibited by mutations in the NS5A sequence (Elazar et al., 2003; Penin et al., 2004b) and abolished by alterations of the zinc-binding site (Tellinghuisen et al., 2004). The recently determined 3-D structure of Domain I suggested the presence of protein, RNA and membrane interaction sites (Moradpour et al., 2005; Tellinghuisen et al., 2005).

The mechanisms by which NS5A regulate HCV replication are not entirely clear. NS5A associates with lipid rafts derived from intracellular membranes through its binding to the C-terminal region of a vesicle-associated membrane-associated protein of 33 kDa (hVAP-33) (Shi et al., 2003; Tu et al., 1999). This interaction appears to be crucial for the formation of the HCV replication complex in connection with lipid rafts (Gao et al., 2004). A recent study in the replicon system proposed a model in which NS5A hyperphosphorylation disrupts the interaction with hVAP- 33 and negatively regulates viral RNA replication (Evans et al., 2004). Another report suggested that the level of NS5A phosphorylation plays an important role in the viral lifecycle by regulating a switch from replication to assembly, whereby hyperphosphorylated forms function to maintain the replication complex in an assembly-incompetent state (Appel et al., 2005). Furthermore, NS5A can interact directly with NS5B, but the mechanism by which NS5A modulates the RdRp activity has not been elucidated (Shimakami et al., 2004). In addition, NS5A was reported to interact with a geranylgeranylated cellular protein (Wang et al., 2005a). This is potentially significant considering that assembly of the viral replication complex has been shown to require geranylgeranylation of one or more host cell proteins (Ye et al., 2003).

Multiple functions have been assigned to NS5A based on its interactions with cellular proteins (Tellinghuisen and Rice, 2002) (see Chapter 9). For instance, NS5A appears to play a role in interferon resistance by binding to and inhibiting PKR, an antiviral effector of interferon-α (Gale et al., 1998). NS5A also bears transcriptional activation functions (Pellerin et al., 2004; Polyak et al., 2001) and appears to be involved in the regulation of cell growth and cellular signaling pathways (Tan and Katze, 2001; Tellinghuisen and Rice, 2002). However, these observations remain to be confirmed in vivo.

NS5B RNA-Dependent RNA Polymerase

NS5B belongs to a class of membrane proteins termed tail-anchored proteins (Ivashkina et al., 2002; Schmidt-Mende et al., 2001) (see Chapter 10). Its C-terminal region (21 residues) forms an α-helical transmembrane domain responsible for post-translational targeting to the cytosolic side of the ER, where the functional protein domain is exposed (Moradpour et al., 2004; Schmidt-Mende et al., 2001). The crystal structure of NS5B revealed that the RdRp has a classical “fingers, palm and thumb” structure formed by its 530 N-terminal aa (Ago et al., 1999; Bressanelli et al., 1999; Lesburg et al., 1999). Interactions between the fingers and thumb subdomains result in a completely encircled catalytic site that ensures synthesis of positive- and negative-strand HCV RNAs (Lesburg et al., 1999). The RdRp is another important target for the development of anti-HCV drugs (Di Marco et al., 2005; Ma et al., 2005; Pawlotsky and McHutchison, 2004; Pawlotsky, 2006).

Interactions between NS5B and cellular components have also been reported. The C-terminus of NS5B can interact with the N-terminus of hVAP-33, and the interaction may play an important role in the formation of the HCV replication complex (Gao et al., 2004; Schmidt-Mende et al., 2001). More recently, NS5B was reported to bind cyclophilin B, a cellular peptidyl-prolyl cis-trans isomerase that apparently regulates HCV replication through modulation of the RNA binding capacity of NS5B (Watashi et al., 2005).

The HCV Lifecycle

Cellular Attachment of HCV Virions and Entry

Many efforts have been made to develop models to identify candidate HCV receptors and study viral binding and entry into target cells. Various cellular and in vivo systems utilizing infected blood samples, virus-like particles produced by expression of structural HCV proteins in insect or mammalian cells, liposomes containing E1–E2, as well as pseudotype particles have yielded a considerable amount of data, although they are not always easy to reconcile. Fig. 3 summarizes the hypothetical HCV lifestyle.

Fig. 3. Hypothetical HCV replication cycle.

Fig. 3

Hypothetical HCV replication cycle. HCV particles bind to the host cells via a specific interaction between the HCV envelope glycoproteins and a yet unknown cellular receptor. Bound particles (more...)

HCV Receptors

Several cell surface molecules have been proposed to mediate HCV binding or HCV binding and internalization.

CD81

Among all putative HCV receptor molecules, CD81 has been the most extensively studied (Pileri et al., 1998). Human CD81 (target of antiproliferative antibody 1, TAPA-1) is a 25-kDa molecule belonging to the tetraspanin or transmembrane 4 superfamily. It is found at the surface of numerous cell types, where it is thought to assemble as homo- and/or heterodimers by means of a conserved hydrophobic interface. CD81 contains four hydrophobic transmembrane regions (TM1 to TM4) and two extracellular loop domains of 28 and 80 aa, respectively: the small extracellular loop (SEL) and the large extracellular loop (LEL). The LEL is located between TM3 and TM4. It is composed of five α-helices and contains four cysteine residues (Kitadokoro et al., 2001). The SEL is needed for optimal surface expression of the LEL (Masciopinto et al., 2001). The intracellular and transmembrane domains of CD81 are highly conserved among different species. In contrast, the LEL is variable, except between humans and chimpanzees, the only two species permissive to HCV infection (Major et al., 2004; Walker, 1997). The CD81 LEL has been shown to mediate binding of HCV through its envelope glycoprotein E2 (Pileri et al., 1998). The integrity of two disulfide bridges is necessary for the CD81-HCV interaction to occur (Petracca et al., 2000), and the site of interaction appears to involve CD81 residues 163, 186, 188 and 196 (Flint et al., 1999; Meola et al., 2000). The E2 domains involved in CD81 binding remain controversial. Early studies suggested the involvement of aa 480–493 and 544–551 in the truncated soluble form of E2 (Flint et al., 1999), whereas a more recent study pointed to a role for two other domains, including aa 613–618 and a second domain spanning the two HVRs (aa 384–410 and 476–480) (Roccasecca et al., 2003).

Several studies argue that cellular factors other than CD81 are required for HCV infection. The expression of human CD81 in a CD81-deficient human hepatoma cell line restored permissiveness to infection with HCV pseudo-particles, but a murine fibroblast cell line expressing human CD81 remained resistant to HCV entry (Cormier et al., 2004). In addition, expression of human CD81 in transgenic mice did not confer susceptibility to HCV infection (Masciopinto et al., 2002). It is possible that the CD81 molecule could act as a post-attachment entry co-receptor and that other cellular factors act together with CD81 to mediate HCV binding and entry into hepatocytes (Cormier et al., 2004).

SR-BI

The scavenger receptor B type I (SR-BI) has been proposed as another candidate receptor for HCV (Scarselli et al., 2002). SR-BI is a 509-aa glycoprotein with a large extracellular loop anchored to the plasma membrane at both N- and C-termini by means of transmembrane domains with short cytoplasmic extensions (Krieger, 2001). SR-BI is a fatty acylated protein located in lipid raft domains. It is expressed at high levels in hepatocytes and steroidogenic cells (Babitt et al., 1997; Krieger, 2001). The natural ligand of SR-BI is high density lipoproteins (HDL). HDLs are internalized through a non-clathrin-dependent endocytosis process that mediates cholesterol uptake and recycling of HDL apoprotein (Silver et al., 2001). HCV genotypes 1a and 1b recombinant E2 envelope glycoproteins were shown to bind HepG2 cells (a human hepatoma cell line that does not express CD81) by interacting with an 82 kDa glycosylated SR-BI molecule (Scarselli et al., 2002). Binding appeared to be highly specific: tranfection of rodent cells with human or tupaia SR-BI (88 % aa identity with human SR-BI) resulted in E2 binding, whereas neither mouse SR-BI (80 % aa identity) nor the closely related human scavenger receptor CD36 (60 % aa identity) bound E2. The SR-BI LEL appeared to be responsible for HCV binding, and HVR1 was recently suggested to be the E2 envelope region involved in the interaction, which was facilitated by serum HDLs (Bartosch et al., 2003b; Scarselli et al., 2002; Voisset et al., 2005). However, the fact that antibodies directed against SR-BI resulted only in a partial blockade of binding suggests that SR-BI is not the only cell surface molecule involved in HCV binding to hepatocytes (Barth et al., 2005).

DC-SIGN and L-SIGN

The dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN or CD209) and the liver/lymph node-specific intercellular adhesion molecule-3 (ICAM-3)-grabbing integrin (L-SIGN or CD209L) have been proposed as tissue-specific capture receptors for HCV present in various cell types that could play a critical role in viral pathogenesis and tissue tropism (Gardner et al., 2003; Lozach et al., 2004; Lozach et al., 2003; Pohlmann et al., 2003). DC-SIGN is a 44-kDa homotetrameric type II integral membrane protein with a short aminoterminal cytoplasmic domain and a carboxy-terminal C-type (calcium-dependent) lectin domain. DC-SIGN is expressed at a high level on myeloid-lineage dendritic cells. Its interaction with ICAM-3 activates T cells (Geijtenbeek et al., 2000). L-SIGN is abundantly expressed at the surface of endothelial cells of the liver and lymph nodes and shares 77% aa sequence identity with DC-SIGN (Bashirova et al., 2001). A rapid internalization of virus-like particles upon capture of HCV pseudo-particles by both DC-SIGN and L-SIGN, presumably via E2 binding, was reported (Ludwig et al., 2004), although this was not observed in another study (Lozach et al., 2004).

LDL-R

The low-density lipoprotein (LDL) receptor (LDL-R) is an endocytic receptor that transports lipoproteins, mainly the cholesterol-rich LDLs, into cells through receptor-mediated endocytosis (Chung and Wasan, 2004). Virus-like particles complexed with LDLs have been reported to enter into cells via the LDL receptor (Agnello et al., 1999; Monazahian et al., 1999). In support of this view, binding of low-density HCV particles recovered from plasma by sucrose gradient sedimentation correlated with the density of LDL receptors at the surface of MOLT-4 cells and fibroblasts, and the binding was inhibited by LDL but not by soluble CD81 (Wunschmann et al., 2000).

Asialoglycoprotein Receptor

The asialoglycoprotein receptor (ASGP-R) has been reported to mediate binding and internalization of structural HCV proteins (C-E1-E2±p7) expressed in a baculovirus system. Cotransfection of a non-permissive mouse fibroblast cell line with cDNAs of both ASGP-R subunits (H1 and H2) restored permissiveness (Saunier et al., 2003).

Glycosaminoglycans

Conservation of positively charged residues in the N-terminus of E2 is in keeping with a possible interaction with heparan sulfate proteoglycans (HSPG) (Barth et al., 2003). E2, in particular its HVR-1, has been shown to bind HSPG with a stronger affinity than other viral envelope glycoproteins, such as human herpes virus 8 or dengue virus envelope proteins. However, glycosaminoglycans are ubiquitously expressed as cell surface molecules. It is conceivable that HSPG could serve as the initial docking site for HCV attachment and the virus is subsequently transferred to another high-affinity receptor (or receptor complex) triggering entry (Barth et al., 2003).

Mechanisms of Cell Entry and Fusion

After attachment, the nucleocapsid of enveloped viruses is released into the cell cytoplasm as a result of a fusion process between viral and cellular membranes. Fusion is mediated by specialized viral proteins and takes place either directly at the plasma membrane or following internalization of the particle into endosomes. The entry process is controlled by viral surface glycoproteins that trigger the changes required for mediating fusion. At least two different classes of fusion proteins (I and II) can be distinguished (Lescar et al., 2001). The flaviviruses enter target cells by receptor-mediated endocytosis and use class II fusion proteins (Lindenbach and Rice, 2001). By analogy, HCV envelope glycoproteins are believed to belong to class II fusion proteins (Yagnik et al., 2000). However, in contrast with other class II fusion proteins, HCV envelope glycoproteins do not appear to require cellular protease cleavage during their transport through the secretory pathway (Op De Beeck et al., 2004). HCV entry into cells is pH-dependent and endocytosis-dependent (Agnello et al., 1999; Bartosch et al., 2003b; Hsu et al., 2003), but the identity of the HCV fusion peptide remains controversial. E1 appeared as a good candidate because sequence analysis suggested the presence of a fusion peptide in its ectodomain (Flint and McKeating, 2000; Rosa et al., 1996). Nevertheless, E2 was shown to share structural homology with class II fusion proteins (Lescar et al., 2001; Yagnik et al., 2000). Crystallographic 3D structure determination and cryo-EM-based studies of both envelope glycoproteins are needed to better understand the mechanisms of HCV fusion.

RNA Translation and Post-Translational Processing

Polyprotein Synthesis

Decapsidation of viral nucleocapsids liberates free positive-strand genomic RNAs into the cell cytoplasm, where they serve, together with newly synthesized RNAs, as messenger RNAs for synthesis of the HCV polyprotein. HCV genome translation is under the control of the IRES, spanning domains II to IV of the 5′ UTR and the first nucleotides of the core-coding region. IRES domain I is not part of the IRES but plays an important role by modulating IRES-dependent translation (Friebe et al., 2001; Luo et al., 2003). The IRES mediates cap-independent internal initiation of HCV polyprotein translation by recruiting both cellular proteins, including eukaryotic initiation factors (eIF) 2 and 3 and viral proteins (Ji et al., 2004; Lukavsky et al., 2000; Otto and Puglisi, 2004). Three distinct translation initiation complexes (40S, 48S and 80S) are generated, as shown by in vitro translation experiments in HeLa S10 cells and rabbit reticulocyte lysates and by ex vivo experiments in mammalian cells (Kong and Sarnow, 2002).

The HCV IRES has the capacity to form a stable pre-initiation complex by directly binding the 40S ribosomal subunit without the need of canonical translation initiation factors (Otto et al., 2002; Spahn et al., 2001). The 40S subunit assembles with eIF3 and this ternary complex joins with eIF2, GTP, and the initiator tRNA to form a 48S particle in which the tRNA is positioned in the P site of the 40S subunit, base-paired to the start codon of the mRNA. Upon hydrolysis of GTP, eIF2 releases the initiator tRNA and dissociates from the complex. A second GTP hydrolysis step involving initiation factor eIF5B then enables the 60S ribosomal subunit to associate, forming a functional 80S ribosome that initiates viral protein synthesis (Ji et al., 2004; Kieft et al., 2001; Otto and Puglisi, 2004; Sizova et al., 1998).

A number of cellular proteins were reported to interact with the 5′ UTR including the polypyrimidine tract-binding protein (PTB) (Ali and Siddiqui, 1995), heterogeneous nuclear ribonucleoprotein L (hnRNP L) (Hahm et al., 1998), La autoantigen (Ali and Siddiqui, 1997), the poly(rC)-binding protein 2 (PCP2) (Spangberg and Schwartz, 1999) and NS1-associated protein 1 (NSAP1) (Kim et al., 2004). The biological significance of these protein-RNA interactions remains unknown. In addition, HCV proteins may affect IRES translational efficiency, including the core protein (Zhang et al., 2002) and non-structural proteins NS4A and NS5B (Kato et al., 2002). The HCV 3′ UTR may also modulate IRES-dependent translation, but this remains controversial (Imbert et al., 2003; Wang et al., 2005b).

Post-Translational Processing

HCV genome translation generates a large precursor polyprotein, which is targeted to the ER membrane for translocation of the E1 ectodomain into the ER lumen, a process mediated by the internal signal sequence located between the core and E1 sequences. Cleavage of the signal sequence by the host signal peptidase yields the immature form of the core protein (P23) (McLauchlan et al., 2002). The signal peptide is further processed by a host signal peptide peptidase (SPP, a presenilintype aspartic protease that resides in the ER membrane) to yield the mature form of the core protein (P21) (Fig. 3) (Penin et al., 2004b). The host signal peptidase also ensures cleavage at the E1–E2 junction in the ER lumen. Additional signal peptidase cleavages at the C-terminal end of E2 and between p7 and NS2 give rise to p7 (Fig. 3). An incomplete cleavage may lead to the production of non-cleaved E2-p7 proteins, the role of which is unknown. E1 and E2 subsequently undergo several maturation steps, including N-glycosylation, conformation and assembly of E1E2 heterodimers (Penin et al., 2004b). Heterogeneous E1E2 aggregates are also produced, but their role in viral particle formation is not known.

The zinc-dependent NS2-3 auto-protease ensures cis-cleavage of NS3 from NS2 (Fig. 2). NS3 needs to assemble with its cofactor NS4A to catalyze cis-cleavage at the NS3-NS4A junction and trans-cleavage at all downstream junctions including NS4A-NS4B, NS4B-NS5A, and NS5A-NS5B (Fig. 2) (Bartenschlager and Lohmann, 2000; Lindenbach and Rice, 2005). The cleavage sites recognized by the NS3-NS4A protease have in common the following sequence: Asp/GluXXXXCys/Thr-Ser/Ala, with trans cleavages occurring downstream of a cysteine residue and the cis cleavage occurring downstream of a threonine residue.

HCV Replication

The HCV Replication Complex

Infection with a positive-strand RNA virus leads to rearrangements of intracellular membranes, a prerequisite to the formation of a replication complex that associates viral proteins, cellular components and nascent RNA strands. The HCV NS4B protein seems to be sufficient to induce the formation of a membranous web or membrane-associated foci (Egger et al., 2002; Gretton et al., 2005). It is not known whether NS4B recruits cellular proteins responsible for vesicle formation or induces vesicle formation by itself. The membranous web is derived from ER membranes (Bartenschlager et al., 2004). It is rich in cholesterol and fatty acids, the degree of saturation of which (that influences membrane fluidity) modulates HCV replication (Kapadia and Chisari, 2005). HCV replication was shown to occur in detergent-resistant membranes that co-localize with caveolin-2, an essential component of lipid raft domains (Shi et al., 2003). Indeed, lipid rafts are involved in the formation of the replication complex, through protein-protein interactions between hVAP-33 and both NS5A and NS5B HCV proteins (Gao et al., 2004; Shi et al., 2003; Tu et al., 1999). Overall, the membranous web consists of small vesicles embedded in a membranous matrix, forming a membrane-associated multiprotein complex that contains all of the nonstructural HCV proteins (Egger et al., 2002).

Mechanism of HCV Replication

The precise mechanisms of HCV replication are still poorly understood. By analogy with other positive-strand RNA viruses, HCV replication is thought to be semi-conservative and asymmetric with two steps, both of which are catalyzed by the NS5B RdRp. The positive-strand genome RNA serves as a template for the synthesis of a negative-strand intermediate of replication during the first step. In the second step, negative-strand RNA serves as a template to produce numerous strands of positive polarity that will subsequently be used for polyprotein translation, synthesis of new intermediates of replication or packaging into new virus particles (Bartenschlager et al., 2004). The positive-strand RNA progeny is transcribed in a five to ten fold in excess compared to negative-strand RNA. NS5B RpRd was initially thought to catalyze primer-dependent initiation of RNA synthesis, either through elongation of a primer hybridized to the RNA template or through a copy-back mechanism (Behrens et al., 1996). More recently, the HCV RdRp was shown to be capable of initiating de novo RNA synthesis under certain experimental conditions (Zhong et al., 2000).

Initiation of RNA strand synthesis at the 3′-end of the plus and minus strands involves domain I of the 5′ UTR, which can form a G/C-rich stem-loop, the 3′ UTR and a cis-acting replication element (5BSL3.2) consisting of 50 bases located in a large predicted cruciform structure at the 3′ end of the HCV NS5B-coding region (You et al., 2004). Initiation of RNA replication is triggered by an interaction between proteins of the replication complex, the 3′ X region of the 3′ UTR, and 5BSL3.2 that forms a pseudoknot structure with a stem-loop in the 3′ UTR (Astier-Gin et al., 2005; Friebe et al., 2005; You et al., 2004). A phosphorylated form of PTB was found in the replication complex and PTB was shown to interact with two conserved stem-loop structures of the 3′ UTR, an interaction thought to modulate RNA replication (Chang and Luo, 2005; Luo, 1999; Luo, 2004). Importantly, inhibition of PTB expression by means of small interfering RNAs reduced the amount of HCV proteins and RNA in HCV replicon-harboring Huh7 cells (Chang and Luo, 2005).

Virus Assembly and Release

Little is known about HCV assembly and release due to the lack of appropriate study models. Different variants of the HCV core protein, which can exist as dimeric, and probably multimeric forms as well, have been shown to be capable of self assembly in yeast in the absence of viral RNA, generating virus-like particles with an average diameter of 35 nm (Acosta-Rivero et al., 2004a; Acosta-Rivero et al., 2004b). Recent reports suggested that the N-terminal portion of the core protein is sufficient for capsid assembly, in particular the two clusters of basic residues (Klein et al., 2005; Klein et al., 2004; Kunkel et al., 2001; Lorenzo et al., 2001; Majeau et al., 2004). In bacterial systems, HCV core proteins efficiently self-assembled to yield nucleocapsid-like particles with a spherical morphology and a diameter of 60 nm, but the presence of a nucleic acid was required (Kunkel et al., 2001). Overall, particle formation is probably initiated by the interaction of the core protein with genomic RNA; HCV core can indeed bind positive-strand RNA in vitro through stem-loop domains I and III and nt 23-41 (Shimoike et al., 1999; Tanaka et al., 2000). It is tempting to speculate that the core-RNA interaction may play a role in the switch from replication to packaging.

Virus-like particles were produced in mammalian cells by using a chimeric virus replicon allowing high-level expression of HCV structural proteins in BHK-21 cell lines (Blanchard et al., 2002). Budding of virus-like particles of 50 nm in diameter in the dilated ER lumen was observed (Blanchard et al., 2003). Transfection of full-length HCV RNA in HeLa G and HepG2 cell lines led to the formation of virus-like particles with a diameter of 45 to 60 nm, which were synthesized and assembled in the cytoplasm and budded into the ER cisternae to form coated particles (Dash et al., 1997; Mizuno et al., 1995). Indeed, the HCV envelope glycoproteins E1 and E2 associate with ER membranes through their transmembrane domains (Cocquerel et al., 1998), suggesting that virus assembly occurs in the ER. Structural proteins have been detected both in the ER and the Golgi apparatus, suggesting that both compartments are involved in later maturation steps (Serafino et al., 2003). Moreover, the presence of N-glycan residues at the surface of HCV particles is also in keeping with a transit via the Golgi apparatus. The mechanisms underlying exportation of mature virions in the pericellular space have yet to be understood. Newly produced virus particles may leave the host cell by the constitutive secretory pathway.

Structure of HCV Virions

HCV is thought to adopt a classical icosahedral scaffold in which glycoproteins E1 and E2 are anchored to the host cell-derived double-layer lipid envelope. Within the envelope is the nucleocapsid which is likely composed of multiple copies of the core protein, forming an internal icosahedral viral coat that encapsidates the viral genomic positive-strand RNA. EM and immuno-EM (IEM) studies of bona fide HCV particles have been hampered by the low amount of viruses in blood and tissues, the failure to efficiently propagate HCV in cell culture, the poor sensitivity of these methods, and antibody cross-reactivity. Visualization of HCV virions or virus-like particles was therefore made essentially from in vitro or non-human in vivo models.

Infection of primary cells or stable cell lines of hepatic or lymphoid origin with sera from HCV-infected patients revealed the presence of spherical virus-like particles (Iacovacci et al., 1997; Serafino et al., 1997; Shimizu et al., 1996). Transfection of Huh7 cells with full-length HCV genomes did not lead to virion production (Pietschmann et al., 2002), but virus-like particles were generated after transfection of HepG2 or Hela G cells (Dash et al., 1997; Mizuno et al., 1995). HCV virus-like particles could also be produced in mammalian cells, by means of recombinant Semliki Forest virus (SFV) or vesicular stomatitis virus (VSV) replicons expressing genes encoding the structural HCV proteins (Blanchard et al., 2003; Ezelle et al., 2002), and in insect cells infected with a recombinant baculovirus expressing HCV structural proteins (Baumert et al., 1998; Luckow and Summers, 1988; Maillard et al., 2001).

Morphology of HCV Particles

Early filtration studies performed in sera from chimpanzees with non-A, non-B hepatitis suggested that the diameter of the causal agent was in the order of 30–60 nm (He et al., 1987; Yuasa et al., 1991). EM and IEM analysis of particles recovered from the blood and liver of infected chimpanzees and patients revealed the presence of spherical particles of 33–70 nm (Bosman et al., 1998; Ishida et al., 2001; Jacob et al., 1990; Kaito et al., 1994; Li et al., 1995; Petit et al., 2003). Detergent treatment of infectious sera yielded 30–40 nm icosahedron-shaped particles containing both the HCV core protein and HCV RNA (Takahashi et al., 1992). Virus-like particles of 45–60 nm was observed in the supernatant of primary cells or stable cell cultures treated with infectious sera and of cell lines transfected with the full-length HCV ORF (Dash et al., 1997; Iacovacci et al., 1997; Mizuno et al., 1995; Serafino et al., 1997; Shimizu et al., 1996). HCV-like particles of 20–60 nm in diameter were also produced by the expression of HCV structural proteins in cell-free systems (Klein et al., 2004), SFV replicons (Blanchard et al., 2002; Blanchard et al., 2003), VSV vectors in rodent BHK-21 cells (Ezelle et al., 2002), bacterial systems (Kunkel et al., 2001; Lorenzo et al., 2001), baculovirus vectors in insect cells (Baumert et al., 1998; Xiang et al., 2002) and yeast expression vectors (Acosta-Rivero et al., 2001; Acosta-Rivero et al., 2004b; Falcon et al., 1999).

The recently developed cell culture system is capable of producing large amounts of infectious HCV virions (Lindenbach et al., 2005b; Wakita et al., 2005; Zhong et al., 2005). Two types of viral particles could be visualized in IEM: particles of 30–35 nm in diameter likely to correspond to the viral nucleocapsids, and particles of 50–60 nm in diameter likely to be the infectious virions (Fig. 4) (Wakita et al., 2005).

Fig. 4. HCV viral particle produced in a tissue culture system from a cloned viral genome (Wakita et al.

Fig. 4

HCV viral particle produced in a tissue culture system from a cloned viral genome (Wakita et al., 2005). Viral particles were generated after transfection of the human (more...)

Circulating Forms of HCV Virions

Plasma Compartmentalization of HCV Particles

HCV was initially reported to have a lower buoyant density than other members of the Flaviviridae family on 20–60% isopycnic sucrose density gradients (1.05 to 1.07 g/ml vs 1.15 to 1.25 g/ml, respectively) (Lindenbach and Rice, 2001; Trestard et al., 1998; Yoshikura et al., 1996). Ultracentrifugation of sera from patients with acute and chronic HCV infection revealed the presence of two populations of HCV particles with a broad range of densities, from 1.06 to 1.25 g/ml. Low-density HCV particles were shown to be principally associated with lipids and lipoproteins and to contain the infectious virus, whereas high-density HCV particles were largely associated with immunoglobulins in the form of immune complexes and supposedly less infectious (Aiyama et al., 1996; Andre et al., 2002; Dienstag et al., 1979; Hijikata et al., 1993; Thomssen et al., 1992). Interestingly, the respective proportions of high- and low-density fractions in infected patients' blood were reported to fluctuate over the course of infection and according to the stage of liver disease (Choo et al., 1995; Hijikata et al., 1993; Kanto et al., 1994; Kanto et al., 1995; Petit et al., 2003).

Non-Enveloped Nucleocapsids

The existence of non-enveloped HCV nucleocapsids during natural infection and their role in the pathophysiology of HCV infection has been debated. Lipo-viroparticles (LVPs) rich in HCV RNA, HCV core protein, triglycerides and apoproteins (especially apoB and apoE) were recently described as large spherical particles of 100 nm, the delipidation of which yielded capsid-like structures (Andre et al., 2002). Non-enveloped nucleocapsids were detected in the serum of infected patients and in hepatocytes from patients and experimentally infected chimpanzees (Falcon et al., 2003a; Falcon et al., 2003b; Maillard et al., 2001). Non-enveloped HCV particles recovered from the plasma of infected individuals had a buoyant density of 1.27 to 1.34 g/ml (Maillard et al., 2001). They were heterogeneous in size, with a diameter of 38–62 nm in EM, and were recently shown to exhibit Fcγ receptor-like activity and bind non-immune IgG (Maillard et al., 2001; Maillard et al., 2004). Whether or not non-enveloped nucleocapsids are infectious remains to be established.

Conclusion

The development of novel anti-HCV therapeutic agents has been stymied by the lack of an efficient in vitro viral infection system and a suitable animal model. Although significant progress has been made through genetic and biochemical approaches in dissecting the molecular processes of HCV replication, our understanding of the viral entry and virion production steps remains rudimentary. Furthermore, HCV exists as “quasispecies” in patients due to its high mutation rate and thus viral resistance will likely be a problem for the emerging small-molecule HCV inhibitors (Pawlotsky, 2003; Pawlotsky, 2006). The recent development of a robust cell culture system for HCV infection may unravel new aspects of HCV replication, which in turn will facilitate the development of specific antivirals that target each stage in the virus life cycle.

References

  1. Acosta-Rivero N, Aguilar JC, Musacchio A, Falcon V, Vina A, de la Rosa MC, Morales J. Characterization of the HCV core virus-like particles produced in the methylotrophic yeast Pichia pastoris. Biochem Biophys Res Commun. 2001;287:122–125. [PubMed: 11549263]
  2. Acosta-Rivero N, Rodriguez A, Musacchio A, Falcon V, Suarez VM, Chavez L, Morales-Grillo J, Duenas-Carrera S. Nucleic acid binding properties and intermediates of HCV core protein multimerization in Pichia pastoris. Biochem Biophys Res Commun. 2004a;323:926–931. [PubMed: 15381089]
  3. Acosta-Rivero N, Rodriguez A, Musacchio A, Falcon V, Suarez VM, Martinez G, Guerra I, Paz-Lago D, Morera Y, de la Rosa MC, et al. In vitro assembly into virus-like particles is an intrinsic quality of Pichia pastoris derived HCV core protein. Biochem Biophys Res Commun. 2004b;325:68–74. [PubMed: 15522201]
  4. Agnello V, Abel G, Elfahal M, Knight GB, Zhang QX. Hepatitis C virus and other flaviviridae viruses enter cells via low density lipoprotein receptor. Proc Natl Acad Sci U S A. 1999;96:12766–12771. [PMC free article: PMC23090] [PubMed: 10535997]
  5. Ago H, Adachi T, Yoshida A, Yamamoto M, Habuka N, Yatsunami K, Miyano M. Crystal structure of the RNA-dependent RNA polymerase of hepatitis C virus. Structure Fold Des. 1999;7:1417–1426. [PubMed: 10574802]
  6. Aiyama T, Yoshioka K, Okumura A, Takayanagi M, Iwata K, Ishikawa T, Kakumu S. Sequence analysis of hypervariable region of hepatitis C virus (HCV) associated with immune complex in patients with chronic HCV infection. J Infect Dis. 1996;174:1316–1320. [PubMed: 8940224]
  7. Ali N, Siddiqui A. Interaction of polypyrimidine tract-binding protein with the 5′ noncoding region of the hepatitis C virus RNA genome and its functional requirement in internal initiation of translation. J Virol. 1995;69:6367–6375. [PMC free article: PMC189536] [PubMed: 7666538]
  8. Ali N, Siddiqui A. The La antigen binds 5′ noncoding region of the hepatitis C virus RNA in the context of the initiator AUG codon and stimulates internal ribosome entry site-mediated translation. Proc Natl Acad Sci U S A. 1997;94:2249–2254. [PMC free article: PMC20073] [PubMed: 9122180]
  9. Andre P, Komurian-Pradel F, Deforges S, Perret M, Berland JL, Sodoyer M, Pol S, Brechot C, Paranhos-Baccala G, Lotteau V. Characterization of low- and very-low-density hepatitis C virus RNA-containing particles. J Virol. 2002;76:6919–6928. [PMC free article: PMC136313] [PubMed: 12072493]
  10. Appel N, Pietschmann T, Bartenschlager R. Mutational analysis of hepatitis C virus nonstructural protein 5A: potential role of differential phosphorylation in RNA replication and identification of a genetically flexible domain. J Virol. 2005;79:3187–3194. [PMC free article: PMC548472] [PubMed: 15709040]
  11. Astier-Gin T, Bellecave P, Litvak S, Ventura M. Template requirements and binding of hepatitis C virus NS5B polymerase during in vitro RNA synthesis from the 3′-end of virus minus-strand RNA. Febs J. 2005;272:3872–3886. [PubMed: 16045758]
  12. Babitt J, Trigatti B, Rigotti A, Smart EJ, Anderson RG, Xu S, Krieger M. Murine SR-BI, a high density lipoprotein receptor that mediates selective lipid uptake, is N-glycosylated and fatty acylated and colocalizes with plasma membrane caveolae. J Biol Chem. 1997;272:13242–13249. [PubMed: 9148942]
  13. Barba G, Harper F, Harada T, Kohara M, Goulinet S, Matsuura Y, Eder G, Schaff Z, Chapman MJ, Miyamura T, Brechot C. Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets. Proc Natl Acad Sci U S A. 1997;94:1200–1205. [PMC free article: PMC19768] [PubMed: 9037030]
  14. Baril M, Brakier-Gingras L. Translation of the F protein of hepatitis C virus is initiated at a non-AUG codon in a +1 reading frame relative to the polyprotein. Nucleic Acids Res. 2005;33:1474–1486. [PMC free article: PMC1062877] [PubMed: 15755749]
  15. Bartenschlager R, Ahlborn-Laake L, Mous J, Jacobsen H. Nonstructural protein 3 of the hepatitis C virus encodes a serine-type protease required for cleavage at the NS3/4 and NS4/5 junctions. J Virol. 1993;67:3835–3844. [PMC free article: PMC237748] [PubMed: 8389908]
  16. Bartenschlager R, Frese M, Pietschmann T. Novel insights into hepatitis C virus replication and persistence. Adv Virus Res. 2004;63:71–180. [PubMed: 15530561]
  17. Bartenschlager R, Lohmann V. Replication of the hepatitis C virus. Baillieres Best Pract Res Clin Gastroenterol. 2000;14:241–254. [PubMed: 10890319]
  18. Bartenschlager R, Lohmann V, Wilkinson T, Koch JO. Complex formation between the NS3 serine-type protease of the hepatitis C virus and NS4A and its importance for polyprotein maturation. J Virol. 1995;69:7519–7528. [PMC free article: PMC189690] [PubMed: 7494258]
  19. Barth H, Cerino R, Arcuri M, Hoffmann M, Schurmann P, Adah MI, Gissler B, Zhao X, Ghisetti V, Lavezzo B, et al. Scavenger receptor class B type I and hepatitis C virus infection of primary tupaia hepatocytes. J Virol. 2005;79:5774–5785. [PMC free article: PMC1082724] [PubMed: 15827192]
  20. Barth H, Schafer C, Adah MI, Zhang F, Linhardt RJ, Toyoda H, Kinoshita- Toyoda A, Toida T, Van Kuppevelt TH, Depla E, et al. Cellular binding of hepatitis C virus envelope glycoprotein E2 requires cell surface heparan sulfate. J Biol Chem. 2003;278:41003–41012. [PubMed: 12867431]
  21. Bartosch B, Dubuisson J, Cosset FL. Infectious hepatitis C virus pseudo-particles containing functional E1–E2 envelope protein complexes. J Exp Med. 2003a;197:633–642. [PMC free article: PMC2193821] [PubMed: 12615904]
  22. Bartosch B, Verney G, Dreux M, Donot P, Morice Y, Penin F, Pawlotsky JM, Lavillette D, Cosset FL. An interplay between hypervariable region 1 of the hepatitis C virus E2 glycoprotein, the scavenger receptor BI, and high-density lipoprotein promotes both enhancement of infection and protection against neutralizing antibodies. J Virol. 2005;79:8217–8229. [PMC free article: PMC1143705] [PubMed: 15956567]
  23. Bartosch B, Vitelli A, Granier C, Goujon C, Dubuisson J, Pascale S, Scarselli E, Cortese R, Nicosia A, Cosset FL. Cell entry of hepatitis C virus requires a set of co-receptors that include the CD81 tetraspanin and the SR-B1 scavenger receptor. J Biol Chem. 2003b;278:41624–41630. [PubMed: 12913001]
  24. Bashirova AA, Geijtenbeek TB, van Duijnhoven GC, van Vliet SJ, Eilering JB, Martin MP, Wu L, Martin TD, Viebig N, Knolle PA, et al. A dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN)-related protein is highly expressed on human liver sinusoidal endothelial cells and promotes HIV-1 infection. J Exp Med. 2001;193:671–678. [PMC free article: PMC2193415] [PubMed: 11257134]
  25. Baumert TF, Ito S, Wong DT, Liang TJ. Hepatitis C virus structural proteins assemble into viruslike particles in insect cells. J Virol. 1998;72:3827–3836. [PMC free article: PMC109606] [PubMed: 9557666]
  26. Beales LP, Rowlands DJ, Holzenburg A. The internal ribosome entry site (IRES) of hepatitis C virus visualized by electron microscopy. RNA. 2001;7:661–670. [PMC free article: PMC1370118] [PubMed: 11350030]
  27. Behrens SE, Tomei L, De Francesco R. Identification and properties of the RNA-dependent RNA polymerase of hepatitis C virus. EMBO J. 1996;15:12– 22. [PMC free article: PMC449913] [PubMed: 8598194]
  28. Blanchard E, Brand D, Trassard S, Goudeau A, Roingeard P. Hepatitis C virus-like particle morphogenesis. J Virol. 2002;76:4073–4079. [PMC free article: PMC136094] [PubMed: 11907246]
  29. Blanchard E, Hourioux C, Brand D, Ait-Goughoulte M, Moreau A, Trassard S, Sizaret PY, Dubois F, Roingeard P. Hepatitis C virus-like particle budding: role of the core protein and importance of its Asp111. J Virol. 2003;77:10131–10138. [PMC free article: PMC224611] [PubMed: 12941925]
  30. Borowski P, Heiland M, Oehlmann K, Becker B, Kornetzky L, Feucht H, Laufs R. Non-structural protein 3 of hepatitis C virus inhibits phosphorylation mediated by cAMP-dependent protein kinase. Eur J Biochem. 1996;237:611–618. [PubMed: 8647104]
  31. Bosman C, Valli MB, Bertolini L, Serafino A, Boldrini R, Marcellini M, Carloni G. Detection of virus-like particles in liver biopsies from HCV-infected patients. Res Virol. 1998;149:311–314. [PubMed: 9879610]
  32. Brass V, Bieck E, Montserret R, Wolk B, Hellings JA, Blum HE, Penin F, Moradpour D. An amino-terminal amphipathic alpha-helix mediates membrane association of the hepatitis C virus nonstructural protein 5A. J Biol Chem. 2002;277:8130–8139. [PubMed: 11744739]
  33. Bressanelli S, Tomei L, Roussel A, Incitti I, Vitale RL, Mathieu M, De Francesco R, Rey FA. Crystal structure of the RNA-dependent RNA polymerase of hepatitis C virus. Proc Natl Acad Sci U S A. 1999;96:13034–13039. [PMC free article: PMC23895] [PubMed: 10557268]
  34. Brinton MA, Dispoto JH. Sequence and secondary structure analysis of the 5′-terminal region of flavivirus genome RNA. Virology. 1988;162:290–299. [PubMed: 2829420]
  35. Brown EA, Zhang H, Ping LH, Lemon SM. Secondary structure of the 5′ nontranslated regions of hepatitis C virus and pestivirus genomic RNAs. Nucleic Acids Res. 1992;20:5041–5045. [PMC free article: PMC334281] [PubMed: 1329037]
  36. Carrere-Kremer S, Montpellier-Pala C, Cocquerel L, Wychowski C, Penin F, Dubuisson J. Subcellular localization and topology of the p7 polypeptide of hepatitis C virus. J Virol. 2002;76:3720–3730. [PMC free article: PMC136108] [PubMed: 11907211]
  37. Chang KS, Luo G. The polypyrimidine tract-binding protein (PTB) is required for efficient replication of hepatitis C virus (HCV) RNA. Virus Res. 2006;115:1–8. [PubMed: 16102869]
  38. Chang SC, Yen JH, Kang HY, Jang MH, Chang MF. Nuclear localization signals in the core protein of hepatitis C virus. Biochem Biophys Res Commun. 1994;205:1284–1290. [PubMed: 7802660]
  39. Cheng JC, Chang MF, Chang SC. Specific interaction between the hepatitis C virus NS5B RNA polymerase and the 3′ end of the viral RNA. J Virol. 1999;73:7044–7049. [PMC free article: PMC112794] [PubMed: 10400807]
  40. Cho HS, Ha NC, Kang LW, Chung KM, Back SH, Jang SK, Oh BH. Crystal structure of RNA helicase from genotype 1b hepatitis C virus. A feasible mechanism of unwinding duplex RNA. J Biol Chem. 1998;273:15045–15052. [PubMed: 9614113]
  41. Choo QL, Richman KH, Han JH, Berger K, Lee C, Dong C, Gallegos C, Coit D, Medina-Selby R, Barr PJ, et al. Genetic organization and diversity of the hepatitis C virus. Proc Natl Acad Sci U S A. 1991;88:2451–2455. [PMC free article: PMC51250] [PubMed: 1848704]
  42. Choo SH, So HS, Cho JM, Ryu WS. Association of hepatitis C virus particles with immunoglobulin: a mechanism for persistent infection. J Gen Virol. 1995;76(Pt 9):2337–2341. [PubMed: 7561774]
  43. Chou AH, Tsai HF, Wu YY, Hu CY, Hwang LH, Hsu PI, Hsu PN. Hepatitis C virus core protein modulates TRAIL-mediated apoptosis by enhancing Bid cleavage and activation of mitochondria apoptosis signaling pathway. J Immunol. 2005;174:2160–2166. [PubMed: 15699147]
  44. Chung NS, Wasan KM. Potential role of the low-density lipoprotein receptor family as mediators of cellular drug uptake. Adv Drug Deliv Rev. 2004;56:1315–1334. [PubMed: 15109771]
  45. Cocquerel L, Meunier JC, Pillez A, Wychowski C, Dubuisson J. A retention signal necessary and sufficient for endoplasmic reticulum localization maps to the transmembrane domain of hepatitis C virus glycoprotein E2. J Virol. 1998;72:2183–2191. [PMC free article: PMC109514] [PubMed: 9499075]
  46. Cocquerel L, Wychowski C, Minner F, Penin F, Dubuisson J. Charged residues in the transmembrane domains of hepatitis C virus glycoproteins play a major role in the processing, subcellular localization, and assembly of these envelope proteins. J Virol. 2000;74:3623–3633. [PMC free article: PMC111872] [PubMed: 10729138]
  47. Coito C, Diamond DL, Neddermann P, Korth MJ, Katze MG. High-throughput screening of the yeast kinome: identification of human serine/threonine protein kinases that phosphorylate the hepatitis C virus NS5A protein. J Virol. 2004;78:3502–3513. [PMC free article: PMC371080] [PubMed: 15016873]
  48. Cormier EG, Tsamis F, Kajumo F, Durso RJ, Gardner JP, Dragic T. CD81 is an entry coreceptor for hepatitis C virus. Proc Natl Acad Sci USA. 2004;101:7270–7274. [PMC free article: PMC409908] [PubMed: 15123813]
  49. Dash S, Halim AB, Tsuji H, Hiramatsu N, Gerber MA. Transfection of HepG2 cells with infectious hepatitis C virus genome. Am J Pathol. 1997;151:363–373. [PMC free article: PMC1858015] [PubMed: 9250150]
  50. Deleersnyder V, Pillez A, Wychowski C, Blight K, Xu J, Hahn YS, Rice CM, Dubuisson J. Formation of native hepatitis C virus glycoprotein complexes. J Virol. 1997;71:697–704. [PMC free article: PMC191102] [PubMed: 8985401]
  51. Di Marco S, Volpari C, Tomei L, Altamura S, Harper S, Narjes F, Koch U, Rowley M, De Francesco R, Migliaccio G, Carfi A. Interdomain communication in hepatitis C virus polymerase abolished by small molecule inhibitors bound to a novel allosteric site. J Biol Chem. 2005;280:29765–29770. [PubMed: 15955819]
  52. Dienstag JL, Bhan AK, Alter HJ, Feinstone SM, Purcell RH. Circulating immune complexes in non-A, non-B hepatitis. Possible masking of viral antigen. Lancet. 1979;1:1265–1267. [PubMed: 87727]
  53. Dumoulin FL, von dem Bussche A, Li J, Khamzina L, Wands JR, Sauerbruch T, Spengler U. Hepatitis C virus NS2 protein inhibits gene expression from different cellular and viral promoters in hepatic and nonhepatic cell lines. Virology. 2003;305:260–266. [PubMed: 12573571]
  54. Egger D, Wolk B, Gosert R, Bianchi L, Blum HE, Moradpour D, Bienz K. Expression of hepatitis C virus proteins induces distinct membrane alterations including a candidate viral replication complex. J Virol. 2002;76:5974–5984. [PMC free article: PMC136238] [PubMed: 12021330]
  55. Elazar M, Cheong KH, Liu P, Greenberg HB, Rice CM, Glenn JS. Amphipathic helix-dependent localization of NS5A mediates hepatitis C virus RNA replication. J Virol. 2003;77:6055–6061. [PMC free article: PMC154017] [PubMed: 12719597]
  56. Elazar M, Liu P, Rice CM, Glenn JS. An N-terminal amphipathic helix in hepatitis C virus (HCV) NS4B mediates membrane association, correct localization of replication complex proteins, and HCV RNA replication. J Virol. 2004;78:11393–11400. [PMC free article: PMC521809] [PubMed: 15452261]
  57. Erdtmann L, Franck N, Lerat H, Le Seyec J, Gilot D, Cannie I, Gripon P, Hibner U, Guguen-Guillouzo C. The hepatitis C virus NS2 protein is an inhibitor of CIDE-B-induced apoptosis. J Biol Chem. 2003;278:18256–18264. [PubMed: 12595532]
  58. Evans MJ, Rice CM, Goff SP. Phosphorylation of hepatitis C virus nonstructural protein 5A modulates its protein interactions and viral RNA replication. Proc Natl Acad Sci USA. 2004;101:13038–13043. [PMC free article: PMC516513] [PubMed: 15326295]
  59. Ezelle HJ, Markovic D, Barber GN. Generation of hepatitis C virus-like particles by use of a recombinant vesicular stomatitis virus vector. J Virol. 2002;76:12325–12334. [PMC free article: PMC136870] [PubMed: 12414973]
  60. Falcon V, Acosta-Rivero N, Chinea G, de la Rosa MC, Menendez I, Duenas-Carrera S, Gra B, Rodriguez A, Tsutsumi V, Shibayama M, et al. Nuclear localization of nucleocapsid-like particles and HCV core protein in hepatocytes of a chronically HCV-infected patient. Biochem Biophys Res Commun. 2003a;310:54–58. [PubMed: 14511647]
  61. Falcon V, Acosta-Rivero N, Chinea G, Gavilondo J, de la Rosa MC, Menendez I, Duenas-Carrera S, Vina A, Garcia W, Gra B, et al. Ultrastructural evidences of HCV infection in hepatocytes of chronically HCVinfected patients. Biochem Biophys Res Commun. 2003b;305:1085–1090. [PubMed: 12767942]
  62. Falcon V, Garcia C, de la Rosa MC, Menendez I, Seoane J, Grillo JM. Ultrastructural and immunocytochemical evidences of core-particle formation in the methylotrophic Pichia pastoris yeast when expressing HCV structural proteins (core-E1). Tissue Cell. 1999;31:117–125. [PubMed: 10445295]
  63. Farci P, Bukh J, Purcell RH. The quasispecies of hepatitis C virus and the host immune response. Springer Semin Immunopathol. 1997;19:5–26. [PubMed: 9266628]
  64. Farci P, Shimoda A, Wong D, Cabezon T, De Gioannis D, Strazzera A, Shimizu Y, Shapiro M, Alter HJ, Purcell RH. Prevention of hepatitis C virus infection in chimpanzees by hyperimmune serum against the hypervariable region 1 of the envelope 2 protein. Proc Natl Acad Sci USA. 1996;93:15394–15399. [PMC free article: PMC26415] [PubMed: 8986822]
  65. Flint M, McKeating JA. The role of the hepatitis C virus glycoproteins in infection. Rev Med Virol. 2000;10:101–117. [PubMed: 10713597]
  66. Flint M, Thomas JM, Maidens CM, Shotton C, Levy S, Barclay WS, McKeating JA. Functional analysis of cell surface-expressed hepatitis C virus E2 glycoprotein. J Virol. 1999;73:6782–6790. [PMC free article: PMC112763] [PubMed: 10400776]
  67. Florese RH, Nagano-Fujii M, Iwanaga Y, Hidajat R, Hotta H. Inhibition of protein synthesis by the nonstructural proteins NS4A and NS4B of hepatitis C virus. Virus Res. 2002;90:119–131. [PubMed: 12457968]
  68. Forton DM, Karayiannis P, Mahmud N, Taylor-Robinson SD, Thomas HC. Identification of unique hepatitis C virus quasispecies in the central nervous system and comparative analysis of internal translational efficiency of brain, liver, and serum variants. J Virol. 2004;78:5170–5183. [PMC free article: PMC400349] [PubMed: 15113899]
  69. Foy E, Li K, Wang C, Sumpter R Jr, Ikeda M, Lemon SM, Gale M Jr. Regulation of interferon regulatory factor-3 by the hepatitis C virus serine protease. Science. 2003;300:1145–1148. [PubMed: 12702807]
  70. Franck N, Le Seyec J, Guguen-Guillouzo C, Erdtmann L. Hepatitis C virus NS2 protein is phosphorylated by the protein kinase CK2 and targeted for degradation to the proteasome. J Virol. 2005;79:2700–2708. [PMC free article: PMC548468] [PubMed: 15708989]
  71. Friebe P, Bartenschlager R. Genetic analysis of sequences in the 3′ nontranslated region of hepatitis C virus that are important for RNA replication. J Virol. 2002;76:5326–5338. [PMC free article: PMC137049] [PubMed: 11991961]
  72. Friebe P, Boudet J, Simorre JP, Bartenschlager R. Kissing-loop interaction in the 3′ end of the hepatitis C virus genome essential for RNA replication. J Virol. 2005;79:380–392. [PMC free article: PMC538730] [PubMed: 15596831]
  73. Friebe P, Lohmann V, Krieger N, Bartenschlager R. Sequences in the 5′ nontranslated region of hepatitis C virus required for RNA replication. J Virol. 2001;75:12047–12057. [PMC free article: PMC116100] [PubMed: 11711595]
  74. Fujita T, Ishido S, Muramatsu S, Itoh M, Hotta H. Suppression of actinomycin D-induced apoptosis by the NS3 protein of hepatitis C virus. Biochem Biophys Res Commun. 1996;229:825–831. [PubMed: 8954979]
  75. Fukutomi T, Zhou Y, Kawai S, Eguchi H, Wands JR, Li J. Hepatitis C virus core protein stimulates hepatocyte growth: correlation with upregulation of wnt-1 expression. Hepatology. 2005;41:1096–1105. [PubMed: 15841445]
  76. Gale MJ Jr, Korth MJ, Katze MG. Repression of the PKR protein kinase by the hepatitis C virus NS5A protein: a potential mechanism of interferon resistance. Clin Diagn Virol. 1998;10:157–162. [PubMed: 9741641]
  77. Gao L, Aizaki H, He JW, Lai MM. Interactions between viral nonstructural proteins and host protein hVAP-33 mediate the formation of hepatitis C virus RNA replication complex on lipid raft. J Virol. 2004;78:3480–3488. [PMC free article: PMC371042] [PubMed: 15016871]
  78. Gardner JP, Durso RJ, Arrigale RR, Donovan GP, Maddon PJ, Dragic T, Olson WC. L-SIGN (CD 209L) is a liver-specific capture receptor for hepatitis C virus. Proc Natl Acad Sci USA. 2003;100:4498–4503. [PMC free article: PMC153584] [PubMed: 12676990]
  79. Geijtenbeek TB, Torensma R, van Vliet SJ, van Duijnhoven GC, Adema GJ, van Kooyk Y, Figdor CG. Identification of DC-SIGN, a novel dendritic cell-specific ICAM-3 receptor that supports primary immune responses. Cell. 2000;100:575–585. [PubMed: 10721994]
  80. Gonzalez ME, Carrasco L. Viroporins. FEBS Lett. 2003;552:28–34. [PubMed: 12972148]
  81. Grakoui A, McCourt DW, Wychowski C, Feinstone SM, Rice CM. Characterization of the hepatitis C virus-encoded serine protease: determination of protease-dependent polyprotein cleavage sites. J Virol. 1993a;67:2832–2843. [PMC free article: PMC237608] [PubMed: 8386278]
  82. Grakoui A, McCourt DW, Wychowski C, Feinstone SM, Rice CM. A second hepatitis C virus-encoded protease. Proc Natl Acad Sci USA. 1993b;90:10583–10587. [PMC free article: PMC47821] [PubMed: 8248148]
  83. Grakoui A, Wychowski C, Lin C, Feinstone SM, Rice CM. Expression and identification of hepatitis C virus polyprotein cleavage products. J Virol. 1993c;67:1385–1395. [PMC free article: PMC237508] [PubMed: 7679746]
  84. Gretton SN, Taylor AI, McLauchlan J. Mobility of the hepatitis C virus NS4B protein on the endoplasmic reticulum membrane and membraneassociated foci. J Gen Virol. 2005;86:1415–1421. [PubMed: 15831953]
  85. Gwack Y, Kim DW, Han JH, Choe J. DNA helicase activity of the hepatitis C virus nonstructural protein 3. Eur J Biochem. 1997;250:47–54. [PubMed: 9431989]
  86. Hahm B, Kim YK, Kim JH, Kim TY, Jang SK. Heterogeneous nuclear ribonucleoprotein L interacts with the 3′ border of the internal ribosomal entry site of hepatitis C virus. J Virol. 1998;72:8782–8788. [PMC free article: PMC110294] [PubMed: 9765422]
  87. Han JH, Shyamala V, Richman KH, Brauer MJ, Irvine B, Urdea MS, Tekamp-Olson P, Kuo G, Choo QL, Houghton M. Characterization of the terminal regions of hepatitis C viral RNA: identification of conserved sequences in the 5′ untranslated region and poly(A) tails at the 3′ end. Proc Natl Acad Sci USA. 1991;88:1711–1715. [PMC free article: PMC51094] [PubMed: 1705704]
  88. Harada S, Watanabe Y, Takeuchi K, Suzuki T, Katayama T, Takebe Y, Saito I, Miyamura T. Expression of processed core protein of hepatitis C virus in mammalian cells. J Virol. 1991;65:3015–3021. [PMC free article: PMC240954] [PubMed: 1709694]
  89. Hassan M, Ghozlan H, Abdel-Kader O. Activation of c-Jun NH2- terminal kinase (JNK) signaling pathway is essential for the stimulation of hepatitis C virus (HCV) non-structural protein 3 (NS3)-mediated cell growth. Virology. 2005;333:324–336. [PubMed: 15721365]
  90. He LF, Alling D, Popkin T, Shapiro M, Alter HJ, Purcell RH. Determining the size of non-A, non-B hepatitis virus by filtration. J Infect Dis. 1987;156:636–640. [PubMed: 3114389]
  91. Hijikata M, Shimizu YK, Kato H, Iwamoto A, Shih JW, Alter HJ, Purcell RH, Yoshikura H. Equilibrium centrifugation studies of hepatitis C virus: evidence for circulating immune complexes. J Virol. 1993;67:1953–1958. [PMC free article: PMC240263] [PubMed: 8383220]
  92. Honda M, Ping LH, Rijnbrand RC, Amphlett E, Clarke B, Rowlands D, Lemon SM. Structural requirements for initiation of translation by internal ribosome entry within genome-length hepatitis C virus RNA. Virology. 1996;222:31–42. [PubMed: 8806485]
  93. Hsu M, Zhang J, Flint M, Logvinoff C, Cheng-Mayer C, Rice CM, McKeating JA. Hepatitis C virus glycoproteins mediate pH-dependent cell entry of pseudotyped retroviral particles. Proc Natl Acad Sci USA. 2003;100:7271–7276. [PMC free article: PMC165865] [PubMed: 12761383]
  94. Hugle T, Fehrmann F, Bieck E, Kohara M, Krausslich HG, Rice CM, Blum HE, Moradpour D. The hepatitis C virus nonstructural protein 4B is an integral endoplasmic reticulum membrane protein. Virology. 2001;284:70–81. [PubMed: 11352669]
  95. Iacovacci S, Manzin A, Barca S, Sargiacomo M, Serafino A, Valli MB, Macioce G, Hassan HJ, Ponzetto A, Clementi M, et al. Molecular characterization and dynamics of hepatitis C virus replication in human fetal hepatocytes infected in vitro. Hepatology. 1997;26:1328–1337. [PubMed: 9362380]
  96. Ide Y, Zhang L, Chen M, Inchauspe G, Bahl C, Sasaguri Y, Padmanabhan R. Characterization of the nuclear localization signal and subcellular distribution of hepatitis C virus nonstructural protein NS5A. Gene. 1996;182:203–211. [PubMed: 8982089]
  97. Imbert I, Dimitrova M, Kien F, Kieny MP, Schuster C. Hepatitis C virus IRES efficiency is unaffected by the genomic RNA 3′ NTR even in the presence of viral structural or non-structural proteins. J Gen Virol. 2003;84:1549–1557. [PubMed: 12771425]
  98. Ishida S, Kaito M, Kohara M, Tsukiyama-Kohora K, Fujita N, Ikoma J, Adachi Y, Watanabe S. Hepatitis C virus core particle detected by immunoelectron microscopy and optical rotation technique. Hepatol Res. 2001;20:335–347. [PubMed: 11404193]
  99. Ito T, Lai MM. Determination of the secondary structure of and cellular protein binding to the 3′-untranslated region of the hepatitis C virus RNA genome. J Virol. 1997;71:8698–8706. [PMC free article: PMC192334] [PubMed: 9343228]
  100. Ivashkina N, Wolk B, Lohmann V, Bartenschlager R, Blum HE, Penin F, Moradpour D. The hepatitis C virus RNA-dependent RNA polymerase membrane insertion sequence is a transmembrane segment. J Virol. 2002;76:13088–13093. [PMC free article: PMC136709] [PubMed: 12438637]
  101. Jacob JR, Burk KH, Eichberg JW, Dreesman GR, Lanford RE. Expression of infectious viral particles by primary chimpanzee hepatocytes isolated during the acute phase of non-A, non-B hepatitis. J Infect Dis. 1990;161:1121–1127. [PubMed: 2111839]
  102. Ji H, Fraser CS, Yu Y, Leary J, Doudna JA. Coordinated assembly of human translation initiation complexes by the hepatitis C virus internal ribosome entry site RNA. Proc Natl Acad Sci USA. 2004;101:16990–16995. [PMC free article: PMC534415] [PubMed: 15563596]
  103. Kadoya H, Nagano-Fujii M, Deng L, Nakazono N, Hotta H. Nonstructural proteins 4A and 4B of hepatitis C virus transactivate the interleukin 8 promoter. Microbiol Immunol. 2005;49:265–273. [PubMed: 15782000]
  104. Kaito M, Watanabe S, Tsukiyama-Kohara K, Yamaguchi K, Kobayashi Y, Konishi M, Yokoi M, Ishida S, Suzuki S, Kohara M. Hepatitis C virus particle detected by immunoelectron microscopic study. J Gen Virol. 1994;75:1755–1760. [PubMed: 7517432]
  105. Kanto T, Hayashi N, Takehara T, Hagiwara H, Mita E, Naito M, Kasahara A, Fusamoto H, Kamada T. Buoyant density of hepatitis C virus recovered from infected hosts: two different features in sucrose equilibrium density-gradient centrifugation related to degree of liver inflammation. Hepatology. 1994;19:296–302. [PubMed: 8294087]
  106. Kanto T, Hayashi N, Takehara T, Hagiwara H, Mita E, Naito M, Kasahara A, Fusamoto H, Kamada T. Density analysis of hepatitis C virus particle population in the circulation of infected hosts: implications for virus neutralization or persistence. J Hepatol. 1995;22:440–448. [PubMed: 7665862]
  107. Kapadia SB, Chisari FV. Hepatitis C virus RNA replication is regulated by host geranylgeranylation and fatty acids. Proc Natl Acad Sci USA. 2005;102:2561–2566. [PMC free article: PMC549027] [PubMed: 15699349]
  108. Kato J, Kato N, Yoshida H, Ono-Nita SK, Shiratori Y, Omata M. Hepatitis C virus NS4A and NS4B proteins suppress translation in vivo. J Med Virol. 2002;66:187–199. [PubMed: 11782927]
  109. Kieft JS, Zhou K, Jubin R, Doudna JA. Mechanism of ribosome recruitment by hepatitis C IRES RNA. RNA. 2001;7:194–206. [PMC free article: PMC1370078] [PubMed: 11233977]
  110. Kim JH, Paek KY, Ha SH, Cho S, Choi K, Kim CS, Ryu SH, Jang SK. A cellular RNA-binding protein enhances internal ribosomal entry site-dependent translation through an interaction downstream of the hepatitis C virus polyprotein initiation codon. Mol Cell Biol. 2004;24:7878–7890. [PMC free article: PMC515056] [PubMed: 15340051]
  111. Kim JL, Morgenstern KA, Griffith JP, Dwyer MD, Thomson JA, Murcko MA, Lin C, Caron PR. Hepatitis C virus NS3 RNA helicase domain with a bound oligonucleotide: the crystal structure provides insights into the mode of unwinding. Structure. 1998;6:89–100. [PubMed: 9493270]
  112. Kim JL, Morgenstern KA, Lin C, Fox T, Dwyer MD, Landro JA, Chambers SP, Markland W, Lepre CA, O'Malley ET, et al. Crystal structure of the hepatitis C virus NS3 protease domain complexed with a synthetic NS4A cofactor peptide. Cell. 1996;87:343–355. [PubMed: 8861917]
  113. Kitadokoro K, Bordo D, Galli G, Petracca R, Falugi F, Abrignani S, Grandi G, Bolognesi M. CD81 extracellular domain 3D structure: insight into the tetraspanin superfamily structural motifs. EMBO J. 2001;20:12–18. [PMC free article: PMC140195] [PubMed: 11226150]
  114. Klein KC, Dellos SR, Lingappa JR. Identification of residues in the hepatitis C virus core protein that are critical for capsid assembly in a cell-free system. J Virol. 2005;79:6814–6826. [PMC free article: PMC1112097] [PubMed: 15890921]
  115. Klein KC, Polyak SJ, Lingappa JR. Unique features of hepatitis C virus capsid formation revealed by de novo cell-free assembly. J Virol. 2004;78:9257–9269. [PMC free article: PMC506955] [PubMed: 15308720]
  116. Kolykhalov AA, Feinstone SM, Rice CM. Identification of a highly conserved sequence element at the 3′ terminus of hepatitis C virus genome RNA. J Virol. 1996;70:3363–3371. [PMC free article: PMC190207] [PubMed: 8648666]
  117. Kong LK, Sarnow P. Cytoplasmic expression of mRNAs containing the internal ribosome entry site and 3′ noncoding region of hepatitis C virus: effects of the 3′ leader on mRNA translation and mRNA stability. J Virol. 2002;76:12457–12462. [PMC free article: PMC136727] [PubMed: 12438571]
  118. Kountouras J, Zavos C, Chatzopoulos D. Apoptosis in hepatitis C. J Viral Hepat. 2003;10:335–342. [PubMed: 12969183]
  119. Krieger M. Scavenger receptor class B type I is a multiligand HDL receptor that influences diverse physiologic systems. J Clin Invest. 2001;108:793–797. [PMC free article: PMC200944] [PubMed: 11560945]
  120. Kunkel M, Lorinczi M, Rijnbrand R, Lemon SM, Watowich SJ. Self-assembly of nucleocapsid-like particles from recombinant hepatitis C virus core protein. J Virol. 2001;75:2119–2129. [PMC free article: PMC114796] [PubMed: 11160716]
  121. Laporte J, Malet I, Andrieu T, Thibault V, Toulme JJ, Wychowski C, Pawlotsky JM, Huraux JM, Agut H, Cahour A. Comparative analysis of translation efficiencies of hepatitis C virus 5′ untranslated regions among intraindividual quasispecies present in chronic infection: opposite behaviors depending on cell type. J Virol. 2000;74:10827–10833. [PMC free article: PMC110962] [PubMed: 11044132]
  122. Laskus T, Radkowski M, Wang LF, Nowicki M, Rakela J. Uneven distribution of hepatitis C virus quasispecies in tissues from subjects with endstage liver disease: confounding effect of viral adsorption and mounting evidence for the presence of low-level extrahepatic replication. J Virol. 2000;74:1014–1017. [PMC free article: PMC111624] [PubMed: 10623766]
  123. Lee H, Shin H, Wimmer E, Paul AV. cis-acting RNA signals in the NS5B C-terminal coding sequence of the hepatitis C virus genome. J Virol. 2004;78:10865–10877. [PMC free article: PMC521798] [PubMed: 15452207]
  124. Lerat H, Shimizu YK, Lemon SM. Cell type-specific enhancement of hepatitis C virus internal ribosome entry site-directed translation due to 5′ nontranslated region substitutions selected during passage of virus in lymphoblastoid cells. J Virol. 2000;74:7024–7031. [PMC free article: PMC112219] [PubMed: 10888641]
  125. Lesburg CA, Cable MB, Ferrari E, Hong Z, Mannarino AF, Weber PC. Crystal structure of the RNA-dependent RNA polymerase from hepatitis C virus reveals a fully encircled active site. Nat Struct Biol. 1999;6:937–943. [PubMed: 10504728]
  126. Lescar J, Roussel A, Wien MW, Navaza J, Fuller SD, Wengler G, Wengler G, Rey FA. The Fusion glycoprotein shell of Semliki Forest virus: an icosahedral assembly primed for fusogenic activation at endosomal pH. Cell. 2001;105:137–148. [PubMed: 11301009]
  127. Levin MK, Gurjar M, Patel SS. A Brownian motor mechanism of translocation and strand separation by hepatitis C virus helicase. Nat Struct Mol Biol. 2005;12:429–435. [PubMed: 15806107]
  128. Li K, Foy E, Ferreon JC, Nakamura M, Ferreon AC, Ikeda M, Ray SC, Gale M Jr, Lemon SM. Immune evasion by hepatitis C virus NS3/4A protease-mediated cleavage of the Toll-like receptor 3 adaptor protein TRIF. Proc Natl Acad Sci USA. 2005;102:2992–2997. [PMC free article: PMC548795] [PubMed: 15710891]
  129. Li X, Jeffers LJ, Shao L, Reddy KR, de Medina M, Scheffel J, Moore B, Schiff ER. Identification of hepatitis C virus by immunoelectron microscopy. J Viral Hepat. 1995;2:227–234. [PubMed: 8745314]
  130. Lin C, Thomson JA, Rice CM. A central region in the hepatitis C virus NS4A protein allows formation of an active NS3-NS4A serine protease complex in vivo and in vitro. J Virol. 1995;69:4373–4380. [PMC free article: PMC189178] [PubMed: 7769699]
  131. Lindenbach BD, Evans MJ, Syder AJ, Wolk B, Tellinghuisen TL, Liu CC, Maruyama T, Hynes RO, Burton DR, McKeating JA, Rice CM. Complete replication of hepatitis C virus in cell culture. Science. 2005a;309:623–626. [PubMed: 15947137]
  132. Lindenbach BD, Evans MJ, Syder AJ, Wolk B, Tellinghuisen TL, Liu CC, Maruyama T, Hynes RO, Burton DR, McKeating JA, Rice CM. Complete Replication of Hepatitis C Virus in Cell Culture. Science. 2005b [PubMed: 15947137]
  133. Lindenbach BD, Rice CM. Flaviviridae: The viruses and Their replication. In: KDM Fields BN, Howley PM, Griffin DE, Lamb RA, Martin MA, Roizman B, Strauss SE, editors. Fields Virology. Philadelphia: Lippincott- Raven; 2001. pp. 991–1042.
  134. Lindenbach BD, Rice CM. Unravelling hepatitis C virus replication from genome to function. Nature. 2005;436:933–938. [PubMed: 16107832]
  135. Lorenzo LJ, Duenas-Carrera S, Falcon V, Acosta-Rivero N, Gonzalez E, de la Rosa MC, Menendez I, Morales J. Assembly of truncated HCV core antigen into virus-like particles in Escherichia coli. Biochem Biophys Res Commun. 2001;281:962–965. [PubMed: 11237755]
  136. Love RA, Parge HE, Wickersham JA, Hostomsky Z, Habuka N, Moomaw EW, Adachi T, Hostomska Z. The crystal structure of hepatitis C virus NS3 protease reveals a trypsin-like fold and a structural zinc binding site. Cell. 1996;87:331–342. [PubMed: 8861916]
  137. Lozach PY, Amara A, Bartosch B, Virelizier JL, Arenzana-Seisdedos F, Cosset FL, Altmeyer R. C-type lectins L-SIGN and DC-SIGN capture and transmit infectious hepatitis C virus pseudotype particles. J Biol Chem. 2004;279:32035–32045. [PubMed: 15166245]
  138. Lozach PY, Lortat-Jacob H, de Lacroix de Lavalette A, Staropoli I, Foung S, Amara A, Houles C, Fieschi F, Schwartz O, Virelizier JL, et al. DC-SIGN and L-SIGN are high affinity binding receptors for hepatitis C virus glycoprotein E2. J Biol Chem. 2003;278:20358–20366. [PubMed: 12609975]
  139. Luckow VA, Summers MD. Signals important for high-level expression of foreign genes in Autographa californica nuclear polyhedrosis virus expression vectors. Virology. 1988;167:56–71. [PubMed: 3142147]
  140. Ludwig IS, Lekkerkerker AN, Depla E, Bosman F, Musters RJ, Depraetere S, van Kooyk Y, Geijtenbeek TB. Hepatitis C virus targets DCSIGN and L-SIGN to escape lysosomal degradation. J Virol. 2004;78:8322–8332. [PMC free article: PMC446128] [PubMed: 15254204]
  141. Lukavsky PJ, Otto GA, Lancaster AM, Sarnow P, Puglisi JD. Structures of two RNA domains essential for hepatitis C virus internal ribosome entry site function. Nat Struct Biol. 2000;7:1105–1110. [PubMed: 11101890]
  142. Lundin M, Monne M, Widell A, Von Heijne G, Persson MA. Topology of the membrane-associated hepatitis C virus protein NS4B. J Virol. 2003;77:5428–5438. [PMC free article: PMC153960] [PubMed: 12692244]
  143. Luo G. Cellular proteins bind to the poly(U) tract of the 3′ untranslated region of hepatitis C virus RNA genome. Virology. 1999;256:105–118. [PubMed: 10087231]
  144. Luo G. Molecular virology of hepatitis C virus. In: Coloacino JM, Heinz BA, editors. Hepatitis Prevetion and Treatment. Basel: Birkhausser; 2004. pp. 67–85.
  145. Luo G, Xin S, Cai Z. Role of the 5′-proximal stem-loop structure of the 5′ untranslated region in replication and translation of hepatitis C virus RNA. J Virol. 2003;77:3312–3318. [PMC free article: PMC149781] [PubMed: 12584356]
  146. Ma H, Leveque V, De Witte A, Li W, Hendricks T, Clausen SM, Cammack N, Klumpp K. Inhibition of native hepatitis C virus replicase by nucleotide and non-nucleoside inhibitors. Virology. 2005;332:8–15. [PubMed: 15661135]
  147. Maillard P, Krawczynski K, Nitkiewicz J, Bronnert C, Sidorkiewicz M, Gounon P, Dubuisson J, Faure G, Crainic R, Budkowska A. Nonenveloped nucleocapsids of hepatitis C virus in the serum of infected patients. J Virol. 2001;75:8240–8250. [PMC free article: PMC115068] [PubMed: 11483769]
  148. Maillard P, Lavergne JP, Siberil S, Faure G, Roohvand F, Petres S, Teillaud JL, Budkowska A. Fcgamma receptor-like activity of hepatitis C virus core protein. J Biol Chem. 2004;279:2430–2437. [PubMed: 14610077]
  149. Majeau N, Gagne V, Boivin A, Bolduc M, Majeau JA, Ouellet D, Leclerc D. The N-terminal half of the core protein of hepatitis C virus is sufficient for nucleocapsid formation. J Gen Virol. 2004;85:971–981. [PubMed: 15039539]
  150. Major ME, Dahari H, Mihalik K, Puig M, Rice CM, Neumann AU, Feinstone SM. Hepatitis C virus kinetics and host responses associated with disease and outcome of infection in chimpanzees. Hepatology. 2004;39:1709–1720. [PubMed: 15185313]
  151. Masciopinto F, Campagnoli S, Abrignani S, Uematsu Y, Pileri P. The small extracellular loop of CD81 is necessary for optimal surface expression of the large loop, a putative HCV receptor. Virus Res. 2001;80:1–10. [PubMed: 11597743]
  152. Masciopinto F, Freer G, Burgio VL, Levy S, Galli-Stampino L, Bendinelli M, Houghton M, Abrignani S, Uematsu Y. Expression of human CD81 in transgenic mice does not confer susceptibility to hepatitis C virus infection. Virology. 2002;304:187–196. [PubMed: 12504561]
  153. Matsuura Y, Suzuki T, Suzuki R, Sato M, Aizaki H, Saito I, Miyamura T. Processing of E1 and E2 glycoproteins of hepatitis C virus expressed in mammalian and insect cells. Virology. 1994;205:141–150. [PubMed: 7975209]
  154. McLauchlan J. Properties of the hepatitis C virus core protein: a structural protein that modulates cellular processes. J Viral Hepat. 2000;7:2–14. [PubMed: 10718937]
  155. McLauchlan J, Lemberg MK, Hope G, Martoglio B. Intramembrane proteolysis promotes trafficking of hepatitis C virus core protein to lipid droplets. EMBO J. 2002;21:3980–3988. [PMC free article: PMC126158] [PubMed: 12145199]
  156. Meola A, Sbardellati A, Bruni Ercole B, Cerretani M, Pezzanera M, Ceccacci A, Vitelli A, Levy S, Nicosia A, Traboni C, et al. Binding of hepatitis C virus E2 glycoprotein to CD81 does not correlate with species permissiveness to infection. J Virol. 2000;74:5933–5938. [PMC free article: PMC112089] [PubMed: 10846074]
  157. Meyer K, Basu A, Saito K, Ray RB, Ray R. Inhibition of hepatitis C virus core protein expression in immortalized human hepatocytes induces cytochrome c-independent increase in Apaf-1 and caspase-9 activation for cell death. Virology. 2005;336:198–207. [PubMed: 15892961]
  158. Miller RH, Purcell RH. Hepatitis C virus shares amino acid sequence similarity with pestiviruses and flaviviruses as well as members of two plant virus supergroups. Proc Natl Acad Sci USA. 1990;87:2057–2061. [PMC free article: PMC53625] [PubMed: 2156259]
  159. Mizuno M, Yamada G, Tanaka T, Shimotohno K, Takatani M, Tsuji T. Virion-like structures in HeLa G cells transfected with the full-length sequence of the hepatitis C virus genome. Gastroenterology. 1995;109:1933–1940. [PubMed: 7498659]
  160. Monazahian M, Bohme I, Bonk S, Koch A, Scholz C, Grethe S, Thomssen R. Low density lipoprotein receptor as a candidate receptor for hepatitis C virus. J Med Virol. 1999;57:223–229. [PubMed: 10022791]
  161. Moradpour D, Brass V, Bieck E, Friebe P, Gosert R, Blum HE, Bartenschlager R, Penin F, Lohmann V. Membrane association of the RNA-dependent RNA polymerase is essential for hepatitis C virus RNA replication. J Virol. 2004;78:13278–13284. [PMC free article: PMC524999] [PubMed: 15542678]
  162. Moradpour D, Brass V, Penin F. Function follows form: The structure of the N-terminal domain of HCV NS5A. Hepatology. 2005;42:732–735. [PubMed: 16116650]
  163. Moriya K, Fujie H, Shintani Y, Yotsuyanagi H, Tsutsumi T, Ishibashi K, Matsuura Y, Kimura S, Miyamura T, Koike K. The core protein of hepatitis C virus induces hepatocellular carcinoma in transgenic mice. Nat Med. 1998;4:1065–1067. [PubMed: 9734402]
  164. Moriya K, Yotsuyanagi H, Shintani Y, Fujie H, Ishibashi K, Matsuura Y, Miyamura T, Koike K. Hepatitis C virus core protein induces hepatic steatosis in transgenic mice. J Gen Virol. 1997;78:1527–1531. [PubMed: 9225025]
  165. Nakajima N, Hijikata M, Yoshikura H, Shimizu YK. Characterization of long-term cultures of hepatitis C virus. J Virol. 1996;70:3325–3329. [PMC free article: PMC190202] [PubMed: 8627819]
  166. Nielsen SU, Bassendine MF, Burt AD, Bevitt DJ, Toms GL. Characterization of the genome and structural proteins of hepatitis C virus resolved from infected human liver. J Gen Virol. 2004;85:1497–1507. [PMC free article: PMC1810391] [PubMed: 15166434]
  167. Nolandt O, Kern V, Muller H, Pfaff E, Theilmann L, Welker R, Krausslich HG. Analysis of hepatitis C virus core protein interaction domains. J Gen Virol. 1997;78:1331–1340. [PubMed: 9191926]
  168. Nunez O, Fernandez-Martinez A, Majano PL, Apolinario A, Gomez-Gonzalo M, Benedicto I, Lopez-Cabrera M, Bosca L, Clemente G, Garcia-Monzon C, Martin-Sanz P. Increased intrahepatic cyclooxygenase 2, matrix metalloprotease 2, and matrix metalloprotease 9 expression is associated with progressive liver disease in chronic hepatitis C virus infection: role of viral core and NS5A proteins. Gut. 2004;53:1665–1672. [PMC free article: PMC1774290] [PubMed: 15479690]
  169. Op De Beeck A, Voisset C, Bartosch B, Ciczora Y, Cocquerel L, Keck Z, Foung S, Cosset FL, Dubuisson J. Characterization of functional hepatitis C virus envelope glycoproteins. J Virol. 2004;78:2994–3002. [PMC free article: PMC353750] [PubMed: 14990718]
  170. Otto GA, Lukavsky PJ, Lancaster AM, Sarnow P, Puglisi JD. Ribosomal proteins mediate the hepatitis C virus IRES-HeLa 40S interaction. RNA. 2002;8:913–923. [PMC free article: PMC1370308] [PubMed: 12166646]
  171. Otto GA, Puglisi JD. The pathway of HCV IRES-mediated translation initiation. Cell. 2004;119:369–380. [PubMed: 15507208]
  172. Park JS, Yang JM, Min MK. Hepatitis C virus nonstructural protein NS4B transforms NIH3T3 cells in cooperation with the Ha-ras oncogene. Biochem Biophys Res Commun. 2000;267:581–587. [PubMed: 10631105]
  173. Pawlotsky JM. Hepatitis C virus genetic variability: pathogenic and clinical implications. Clin Liver Dis. 2003;7:45–66. [PubMed: 12691458]
  174. Pawlotsky JM. Therapy of hepatitis C: from empiricism to cure. Hepatology . 2006;43(Suppl 1):S207–S220. [PubMed: 16447262]
  175. Pawlotsky JM, Germanidis G. The non-structural 5A protein of hepatitis C virus. J Viral Hepat. 1999;6:343–356. [PubMed: 10607250]
  176. Pawlotsky JM, McHutchison JG. Hepatitis C. Development of new drugs and clinical trials: promises and pitfalls. Summary of an AASLD hepatitis single topic conference, Chicago, IL, February 27–March 1, 2003. Hepatology. 2004;39:554–567. [PubMed: 14768012]
  177. Pellerin M, Lopez-Aguirre Y, Penin F, Dhumeaux D, Pawlotsky JM. Hepatitis C virus quasispecies variability modulates nonstructural protein 5A transcriptional activation, pointing to cellular compartmentalization of virushost interactions. J Virol. 2004;78:4617–4627. [PMC free article: PMC387712] [PubMed: 15078944]
  178. Penin F, Brass V, Appel N, Ramboarina S, Montserret R, Ficheux D, Blum HE, Bartenschlager R, Moradpour D. Structure and function of the membrane anchor domain of hepatitis C virus nonstructural protein 5A. J Biol Chem. 2004a;279:40835–40843. [PubMed: 15247283]
  179. Penin F, Combet C, Germanidis G, Frainais PO, Deleage G, Pawlotsky JM. Conservation of the conformation and positive charges of hepatitis C virus E2 envelope glycoprotein hypervariable region 1 points to a role in cell attachment. J Virol. 2001;75:5703–5710. [PMC free article: PMC114285] [PubMed: 11356980]
  180. Penin F, Dubuisson J, Rey FA, Moradpour D, Pawlotsky JM. Structural biology of hepatitis C virus. Hepatology. 2004b;39:5–19. [PubMed: 14752815]
  181. Petit JM, Benichou M, Duvillard L, Jooste V, Bour JB, Minello A, Verges B, Brun JM, Gambert P, Hillon P. Hepatitis C virus-associated hypobetalipoproteinemia is correlated with plasma viral load, steatosis, and liver fibrosis. Am J Gastroenterol. 2003;98:1150–1154. [PubMed: 12809841]
  182. Petracca R, Falugi F, Galli G, Norais N, Rosa D, Campagnoli S, Burgio V, Di Stasio E, Giardina B, Houghton M, et al. Structure-function analysis of hepatitis C virus envelope-CD81 binding. J Virol. 2000;74:4824–4830. [PMC free article: PMC112005] [PubMed: 10775621]
  183. Piccininni S, Varaklioti A, Nardelli M, Dave B, Raney KD, McCarthy JE. Modulation of the hepatitis C virus RNA-dependent RNA polymerase activity by the non-structural (NS) 3 helicase and the NS4B membrane protein. J Biol Chem. 2002;277:45670–45679. [PubMed: 12235135]
  184. Pietschmann T, Lohmann V, Kaul A, Krieger N, Rinck G, Rutter G, Strand D, Bartenschlager R. Persistent and transient replication of fulllength hepatitis C virus genomes in cell culture. J Virol. 2002;76:4008–4021. [PMC free article: PMC136109] [PubMed: 11907240]
  185. Pileri P, Uematsu Y, Campagnoli S, Galli G, Falugi F, Petracca R, Weiner AJ, Houghton M, Rosa D, Grandi G, Abrignani S. Binding of hepatitis C virus to CD81. Science. 1998;282:938–941. [PubMed: 9794763]
  186. Pohlmann S, Zhang J, Baribaud F, Chen Z, Leslie GJ, Lin G, Granelli- Piperno A, Doms RW, Rice CM, McKeating JA. Hepatitis C virus glycoproteins interact with DC-SIGN and DC-SIGNR. J Virol. 2003;77:4070–4080. [PMC free article: PMC150620] [PubMed: 12634366]
  187. Polyak SJ, Khabar KS, Paschal DM, Ezelle HJ, Duverlie G, Barber GN, Levy DE, Mukaida N, Gretch DR. Hepatitis C virus nonstructural 5A protein induces interleukin-8, leading to partial inhibition of the interferon-induced antiviral response. J Virol. 2001;75:6095–6106. [PMC free article: PMC114325] [PubMed: 11390611]
  188. Polyak SJ, Paschal DM, McArdle S, Gale MJ Jr, Moradpour D, Gretch DR. Characterization of the effects of hepatitis C virus nonstructural 5A protein expression in human cell lines and on interferon-sensitive virus replication. Hepatology. 1999;29:1262–1271. [PubMed: 10094974]
  189. Ray RB, Lagging LM, Meyer K, Steele R, Ray R. Transcriptional regulation of cellular and viral promoters by the hepatitis C virus core protein. Virus Res. 1995;37:209–220. [PubMed: 8533458]
  190. Roccasecca R, Ansuini H, Vitelli A, Meola A, Scarselli E, Acali S, Pezzanera M, Ercole BB, McKeating J, Yagnik A, et al. Binding of the hepatitis C virus E2 glycoprotein to CD81 is strain specific and is modulated by a complex interplay between hypervariable regions 1 and 2. J Virol. 2003;77:1856–1867. [PMC free article: PMC140892] [PubMed: 12525620]
  191. Rosa D, Campagnoli S, Moretto C, Guenzi E, Cousens L, Chin M, Dong C, Weiner AJ, Lau JY, Choo QL, et al. A quantitative test to estimate neutralizing antibodies to the hepatitis C virus: cytofluorimetric assessment of envelope glycoprotein 2 binding to target cells. Proc Natl Acad Sci USA. 1996;93:1759–1763. [PMC free article: PMC39854] [PubMed: 8700831]
  192. Sakai A, Claire MS, Faulk K, Govindarajan S, Emerson SU, Purcell RH, Bukh J. The p7 polypeptide of hepatitis C virus is critical for infectivity and contains functionally important genotype-specific sequences. Proc Natl Acad Sci USA. 2003;100:11646–11651. [PMC free article: PMC208812] [PubMed: 14504405]
  193. Sakamuro D, Furukawa T, Takegami T. Hepatitis C virus nonstructural protein NS3 transforms NIH 3T3 cells. J Virol. 1995;69:3893–3896. [PMC free article: PMC189112] [PubMed: 7745741]
  194. Santolini E, Migliaccio G, La Monica N. Biosynthesis and biochemical properties of the hepatitis C virus core protein. J Virol. 1994;68:3631–3641. [PMC free article: PMC236867] [PubMed: 8189501]
  195. Santolini E, Pacini L, Fipaldini C, Migliaccio G, Monica N. The NS2 protein of hepatitis C virus is a transmembrane polypeptide. J Virol. 1995;69:7461–7471. [PMC free article: PMC189684] [PubMed: 7494252]
  196. Satoh S, Hirota M, Noguchi T, Hijikata M, Handa H, Shimotohno K. Cleavage of hepatitis C virus nonstructural protein 5A by a caspase-like protease(s) in mammalian cells. Virology. 2000;270:476–487. [PubMed: 10793006]
  197. Saunier B, Triyatni M, Ulianich L, Maruvada P, Yen P, Kohn LD. Role of the asialoglycoprotein receptor in binding and entry of hepatitis C virus structural proteins in cultured human hepatocytes. J Virol. 2003;77:546–559. [PMC free article: PMC140572] [PubMed: 12477859]
  198. Scarselli E, Ansuini H, Cerino R, Roccasecca RM, Acali S, Filocamo G, Traboni C, Nicosia A, Cortese R, Vitelli A. The human scavenger receptor class B type I is a novel candidate receptor for the hepatitis C virus. EMBO J. 2002;21:5017–5025. [PMC free article: PMC129051] [PubMed: 12356718]
  199. Schmidt-Mende J, Bieck E, Hugle T, Penin F, Rice CM, Blum HE, Moradpour D. Determinants for membrane association of the hepatitis C virus RNA-dependent RNA polymerase. J Biol Chem. 2001;276:44052–44063. [PubMed: 11557752]
  200. Schwer B, Ren S, Pietschmann T, Kartenbeck J, Kaehlcke K, Bartenschlager R, Yen TS, Ott M. Targeting of hepatitis C virus core protein to mitochondria through a novel C-terminal localization motif. J Virol. 2004;78:7958–7968. [PMC free article: PMC446112] [PubMed: 15254168]
  201. Serafino A, Valli MB, Alessandrini A, Ponzetto A, Carloni G, Bertolini L. Ultrastructural observations of viral particles within hepatitis C virusinfected human B lymphoblastoid cell line. Res Virol. 1997;148:153–159. [PubMed: 9108618]
  202. Serafino A, Valli MB, Andreola F, Crema A, Ravagnan G, Bertolini L, Carloni G. Suggested role of the Golgi apparatus and endoplasmic reticulum for crucial sites of hepatitis C virus replication in human lymphoblastoid cells infected in vitro. J Med Virol. 2003;70:31–41. [PubMed: 12629641]
  203. Shi ST, Lee KJ, Aizaki H, Hwang SB, Lai MM. Hepatitis C virus RNA replication occurs on a detergent-resistant membrane that cofractionates with caveolin-2. J Virol. 2003;77:4160–4168. [PMC free article: PMC150636] [PubMed: 12634374]
  204. Shih CM, Lo SJ, Miyamura T, Chen SY, Lee YH. Suppression of hepatitis B virus expression and replication by hepatitis C virus core protein in HuH-7 cells. J Virol. 1993;67:5823–5832. [PMC free article: PMC238000] [PubMed: 8396658]
  205. Shimakami T, Hijikata M, Luo H, Ma YY, Kaneko S, Shimotohno K, Murakami S. Effect of interaction between hepatitis C virus NS5A and NS5B on hepatitis C virus RNA replication with the hepatitis C virus replicon. J Virol. 2004;78:2738–2748. [PMC free article: PMC353754] [PubMed: 14990694]
  206. Shimizu YK, Feinstone SM, Kohara M, Purcell RH, Yoshikura H. Hepatitis C virus: detection of intracellular virus particles by electron microscopy. Hepatology. 1996;23:205–209. [PubMed: 8591842]
  207. Shimizu YK, Igarashi H, Kanematu T, Fujiwara K, Wong DC, Purcell RH, Yoshikura H. Sequence analysis of the hepatitis C virus genome recovered from serum, liver, and peripheral blood mononuclear cells of infected chimpanzees. J Virol. 1997;71:5769–5773. [PMC free article: PMC191830] [PubMed: 9223464]
  208. Shimoike T, Mimori S, Tani H, Matsuura Y, Miyamura T. Interaction of hepatitis C virus core protein with viral sense RNA and suppression of its translation. J Virol. 1999;73:9718–9725. [PMC free article: PMC113018] [PubMed: 10559281]
  209. Silver DL, Wang N, Xiao X, Tall AR. High density lipoprotein (HDL) particle uptake mediated by scavenger receptor class B type 1 results in selective sorting of HDL cholesterol from protein and polarized cholesterol secretion. J Biol Chem. 2001;276:25287–25293. [PubMed: 11301333]
  210. Simons JN, Leary TP, Dawson GJ, Pilot-Matias TJ, Muerhoff AS, Schlauder GG, Desai SM, Mushahwar IK. Isolation of novel virus-like sequences associated with human hepatitis. Nat Med. 1995a;1:564–569. [PubMed: 7585124]
  211. Simons JN, Pilot-Matias TJ, Leary TP, Dawson GJ, Desai SM, Schlauder GG, Muerhoff AS, Erker JC, Buijk SL, Chalmers ML, et al. Identification of two flavivirus-like genomes in the GB hepatitis agent. Proc Natl Acad Sci USA. 1995b;92:3401–3405. [PMC free article: PMC42174] [PubMed: 7724574]
  212. Sizova DV, Kolupaeva VG, Pestova TV, Shatsky IN, Hellen CU. Specific interaction of eukaryotic translation initiation factor 3 with the 5′ nontranslated regions of hepatitis C virus and classical swine fever virus RNAs. J Virol. 1998;72:4775–4782. [PMC free article: PMC110013] [PubMed: 9573242]
  213. Spahn CM, Kieft JS, Grassucci RA, Penczek PA, Zhou K, Doudna JA, Frank J. Hepatitis C virus IRES RNA-induced changes in the conformation of the 40s ribosomal subunit. Science. 2001;291:1959–1962. [PubMed: 11239155]
  214. Spangberg K, Schwartz S. Poly(C)-binding protein interacts with the hepatitis C virus 5′ untranslated region. J Gen Virol. 1999;80:1371–1376. [PubMed: 10374953]
  215. Sumpter R Jr, Loo YM, Foy E, Li K, Yoneyama M, Fujita T, Lemon SM, Gale M Jr. Regulating intracellular antiviral defense and permissiveness to hepatitis C virus RNA replication through a cellular RNA helicase, RIG-I. J Virol. 2005;79:2689–2699. [PMC free article: PMC548482] [PubMed: 15708988]
  216. Suzuki R, Matsuura Y, Suzuki T, Ando A, Chiba J, Harada S, Saito I, Miyamura T. Nuclear localization of the truncated hepatitis C virus core protein with its hydrophobic C terminus deleted. J Gen Virol. 1995;76:53–61. [PubMed: 7844542]
  217. Suzuki R, Sakamoto S, Tsutsumi T, Rikimaru A, Tanaka K, Shimoike T, Moriishi K, Iwasaki T, Mizumoto K, Matsuura Y, et al. Molecular determinants for subcellular localization of hepatitis C virus core protein. J Virol. 2005;79:1271–1281. [PMC free article: PMC538550] [PubMed: 15613354]
  218. Tai CL, Chi WK, Chen DS, Hwang LH. The helicase activity associated with hepatitis C virus nonstructural protein 3 (NS3). J Virol. 1996;70:8477–8484. [PMC free article: PMC190938] [PubMed: 8970970]
  219. Takahashi K, Kishimoto S, Yoshizawa H, Okamoto H, Yoshikawa A, Mishiro S. p26 protein and 33-nm particle associated with nucleocapsid of hepatitis C virus recovered from the circulation of infected hosts. Virology. 1992;191:431–434. [PubMed: 1329328]
  220. Tan SL, Katze MG. How hepatitis C virus counteracts the interferon response: the jury is still out on NS5A. Virology. 2001;284:1–12. [PubMed: 11352662]
  221. Tanaka T, Kato N, Cho MJ, Shimotohno K. A novel sequence found at the 3′ terminus of hepatitis C virus genome. Biochem Biophys Res Commun. 1995;215:744–749. [PubMed: 7488017]
  222. Tanaka T, Kato N, Cho MJ, Sugiyama K, Shimotohno K. Structure of the 3′ terminus of the hepatitis C virus genome. J Virol. 1996;70:3307–3312. [PMC free article: PMC190199] [PubMed: 8627816]
  223. Tanaka Y, Shimoike T, Ishii K, Suzuki R, Suzuki T, Ushijima H, Matsuura Y, Miyamura T. Selective binding of hepatitis C virus core protein to synthetic oligonucleotides corresponding to the 5′ untranslated region of the viral genome. Virology. 2000;270:229–236. [PubMed: 10772995]
  224. Tanji Y, Hijikata M, Satoh S, Kaneko T, Shimotohno K. Hepatitis C virus-encoded nonstructural protein NS4A has versatile functions in viral protein processing. J Virol. 1995;69:1575–1581. [PMC free article: PMC188752] [PubMed: 7853491]
  225. Tellinghuisen TL, Marcotrigiano J, Gorbalenya AE, Rice CM. The NS5A protein of hepatitis C virus is a zinc metalloprotein. J Biol Chem. 2004;279:48576–48587. [PubMed: 15339921]
  226. Tellinghuisen TL, Marcotrigiano J, Rice CM. Structure of the zinc-binding domain of an essential component of the hepatitis C virus replicase. Nature. 2005;435:374–379. [PMC free article: PMC1440517] [PubMed: 15902263]
  227. Tellinghuisen TL, Rice CM. Interaction between hepatitis C virus proteins and host cell factors. Curr Opin Microbiol. 2002;5:419–427. [PubMed: 12160863]
  228. Thomssen R, Bonk S, Propfe C, Heermann KH, Kochel HG, Uy A. Association of hepatitis C virus in human sera with beta-lipoprotein. Med Microbiol Immunol (Berl). 1992;181:293–300. [PubMed: 1335546]
  229. Thurner C, Witwer C, Hofacker IL, Stadler PF. Conserved RNA secondary structures in Flaviviridae genomes. J Gen Virol. 2004;85:1113–1124. [PubMed: 15105528]
  230. Tomei L, Failla C, Santolini E, De Francesco R, La Monica N. NS3 is a serine protease required for processing of hepatitis C virus polyprotein. J Virol. 1993;67:4017–4026. [PMC free article: PMC237769] [PubMed: 7685406]
  231. Trestard A, Bacq Y, Buzelay L, Dubois F, Barin F, Goudeau A, Roingeard P. Ultrastructural and physicochemical characterization of the hepatitis C virus recovered from the serum of an agammaglobulinemic patient. Arch Virol. 1998;143:2241–2245. [PubMed: 9856105]
  232. Tu H, Gao L, Shi ST, Taylor DR, Yang T, Mircheff AK, Wen Y, Gorbalenya AE, Hwang SB, Lai MM. Hepatitis C virus RNA polymerase and NS5A complex with a SNARE-like protein. Virology. 1999;263:30– 41. [PubMed: 10544080]
  233. Voisset C, Callens N, Blanchard E, Op De Beeck A, Dubuisson J, Vu-Dac N. High density lipoproteins facilitate hepatitis C virus entry through the scavenger receptor class B type I. J Biol Chem. 2005;280:7793–7799. [PubMed: 15632171]
  234. Wakita T, Pietschmann T, Kato T, Date T, Miyamoto M, Zhao Z, Murthy K, Habermann A, Krausslich HG, Mizokami M, et al. Production of infectious hepatitis C virus in tissue culture from a cloned viral genome. Nat Med. 2005;11:791–796. [PMC free article: PMC2918402] [PubMed: 15951748]
  235. Walewski JL, Keller TR, Stump DD, Branch AD. Evidence for a new hepatitis C virus antigen encoded in an overlapping reading frame. RNA. 2001;7:710–721. [PMC free article: PMC1370123] [PubMed: 11350035]
  236. Walker CM. Comparative features of hepatitis C virus infection in humans and chimpanzees. Springer Semin Immunopathol. 1997;19:85–98. [PubMed: 9266633]
  237. Wang C, Gale M Jr, Keller BC, Huang H, Brown MS, Goldstein JL, Ye J. Identification of FBL2 as a geranylgeranylated cellular protein required for hepatitis C virus RNA replication. Mol Cell. 2005a;18:425–434. [PubMed: 15893726]
  238. Wang C, Le SY, Ali N, Siddiqui A. An RNA pseudoknot is an essential structural element of the internal ribosome entry site located within the hepatitis C virus 5′ noncoding region. RNA. 1995;1:526–537. [PMC free article: PMC1482419] [PubMed: 7489514]
  239. Wang H, Shen XT, Ye R, Lan SY, Xiang L, Yuan ZH. Roles of the polypyrimidine tract and 3′ noncoding region of hepatitis C virus RNA in the internal ribosome entry site-mediated translation. Arch Virol. 2005b;150:1085–1099. [PubMed: 15747050]
  240. Watashi K, Ishii N, Hijikata M, Inoue D, Murata T, Miyanari Y, Shimotohno K. Cyclophilin B is a functional regulator of hepatitis C virus RNA polymerase. Mol Cell. 2005;19:111–122. [PubMed: 15989969]
  241. Weiner AJ, Christopherson C, Hall JE, Bonino F, Saracco G, Brunetto MR, Crawford K, Marion CD, Crawford KA, Venkatakrishna S, et al. Sequence variation in hepatitis C viral isolates. J Hepatol . 1991;13(Suppl 4):S6–14. [PubMed: 1668332]
  242. Wunschmann S, Medh JD, Klinzmann D, Schmidt WN, Stapleton JT. Characterization of hepatitis C virus (HCV) and HCV E2 interactions with CD81 and the low-density lipoprotein receptor. J Virol. 2000;74:10055–10062. [PMC free article: PMC102044] [PubMed: 11024134]
  243. Xiang J, Wunschmann S, George SL, Klinzman D, Schmidt WN, LaBrecque DR, Stapleton JT. Recombinant hepatitis C virus-like particles expressed by baculovirus: utility in cell-binding and antibody detection assays. J Med Virol. 2002;68:537–543. [PubMed: 12376962]
  244. Yagnik AT, Lahm A, Meola A, Roccasecca RM, Ercole BB, Nicosia A, Tramontano A. A model for the hepatitis C virus envelope glycoprotein E2. Proteins. 2000;40:355–366. [PubMed: 10861927]
  245. Yamaga AK, Ou JH. Membrane topology of the hepatitis C virus NS2 protein. J Biol Chem. 2002;277:33228–33234. [PubMed: 12082096]
  246. Yan Y, Li Y, Munshi S, Sardana V, Cole JL, Sardana M, Steinkuehler C, Tomei L, De Francesco R, Kuo LC, Chen Z. Complex of NS3 protease and NS4A peptide of BK strain hepatitis C virus: a 2.2 A resolution structure in a hexagonal crystal form. Protein Sci. 1998;7:837–847. [PMC free article: PMC2143993] [PubMed: 9568891]
  247. Yao N, Hesson T, Cable M, Hong Z, Kwong AD, Le HV, Weber PC. Structure of the hepatitis C virus RNA helicase domain. Nat Struct Biol. 1997;4:463–467. [PubMed: 9187654]
  248. Yasui K, Wakita T, Tsukiyama-Kohara K, Funahashi SI, Ichikawa M, Kajita T, Moradpour D, Wands JR, Kohara M. The native form and maturation process of hepatitis C virus core protein. J Virol. 1998;72:6048–6055. [PMC free article: PMC110410] [PubMed: 9621068]
  249. Ye J, Wang C, Sumpter R Jr, Brown MS, Goldstein JL, Gale M Jr. Disruption of hepatitis C virus RNA replication through inhibition of host protein geranylgeranylation. Proc Natl Acad Sci USA. 2003;100:15865–15870. [PMC free article: PMC307659] [PubMed: 14668447]
  250. Yi M, Lemon SM. 3′ nontranslated RNA signals required for replication of hepatitis C virus RNA. J Virol. 2003a;77:3557–3568. [PMC free article: PMC149512] [PubMed: 12610131]
  251. Yi M, Lemon SM. Structure-function analysis of the 3′ stem-loop of hepatitis C virus genomic RNA and its role in viral RNA replication. RNA. 2003b;9:331–345. [PMC free article: PMC1370400] [PubMed: 12592007]
  252. Yoshikura H, Hijikata M, Nakajima N, Shimizu YK. Replication of hepatitis C virus. J Viral Hepat. 1996;3:3–10. [PubMed: 8736234]
  253. You S, Stump DD, Branch AD, Rice CM. A cis-acting replication element in the sequence encoding the NS5B RNA-dependent RNA polymerase is required for hepatitis C virus RNA replication. J Virol. 2004;78:1352–1366. [PMC free article: PMC321395] [PubMed: 14722290]
  254. Yuasa T, Ishikawa G, Manabe S, Sekiguchi S, Takeuchi K, Miyamura T. The particle size of hepatitis C virus estimated by filtration through microporous regenerated cellulose fibre. J Gen Virol. 1991;72:2021–2024. [PubMed: 1714947]
  255. Zhang C, Cai Z, Kim YC, Kumar R, Yuan F, Shi PY, Kao C, Luo G. Stimulation of hepatitis C virus (HCV) nonstructural protein 3 (NS3) helicase activity by the NS3 protease domain and by HCV RNA-dependent RNA polymerase. J Virol. 2005;79:8687–8697. [PMC free article: PMC1168731] [PubMed: 15994762]
  256. Zhang J, Yamada O, Yoshida H, Iwai T, Araki H. Autogenous translational inhibition of core protein: implication for switch from translation to RNA replication in hepatitis C virus. Virology. 2002;293:141–150. [PubMed: 11853407]
  257. Zhong J, Gastaminza P, Cheng G, Kapadia S, Kato T, Burton DR, Wieland SF, Uprichard SL, Wakita T, Chisari FV. Robust hepatitis C virus infection in vitro. Proc Natl Acad Sci USA. 2005;102:9294–9299. [PMC free article: PMC1166622] [PubMed: 15939869]
  258. Zhong W, Uss AS, Ferrari E, Lau JY, Hong Z. De novo initiation of RNA synthesis by hepatitis C virus nonstructural protein 5B polymerase. J Virol. 2000;74:2017–2022. [PMC free article: PMC111680] [PubMed: 10644375]
  259. Zibert A, Kraas W, Meisel H, Jung G, Roggendorf M. Epitope mapping of antibodies directed against hypervariable region 1 in acute selflimiting and chronic infections due to hepatitis C virus. J Virol. 1997;71:4123–4127. [PMC free article: PMC191569] [PubMed: 9094694]
Copyright © 2006, Horizon Bioscience.
Bookshelf ID: NBK1630PMID: 21250393

Views

Related information

  • PMC
    PubMed Central citations
  • PubMed
    Links to PubMed

Similar articles in PubMed

See reviews...See all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...