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Silent Information Regulator Proteins, Saccharomyces cerevisiae

A set of nuclear proteins in SACCHAROMYCES CEREVISIAE that are required for the transcriptional repression of the silent mating type loci. They mediate the formation of silenced CHROMATIN and repress both transcription and recombination at other loci as well. They are comprised of 4 non-homologous, interacting proteins, Sir1p, Sir2p, Sir3p, and Sir4p. Sir2p, an NAD-dependent HISTONE DEACETYLASE, is the founding member of the family of SIRTUINS.

Year introduced: 2003


Silent Mutation

A change to a DNA SEQUENCE that doesn't change the AMINO ACID SEQUENCE of the protein made.

Year introduced: 2016



A homologous family of regulatory enzymes that are structurally related to the protein silent mating type information regulator 2 (Sir2) found in Saccharomyces cerevisiae. Sirtuins contain a central catalytic core region which binds NAD. Several of the sirtuins utilize NAD to deacetylate proteins such as HISTONES and are categorized as GROUP III HISTONE DEACETYLASES. Several other sirtuin members utilize NAD to transfer ADP-RIBOSE to proteins and are categorized as MONO ADP-RIBOSE TRANSFERASES, while a third group of sirtuins appears to have both deacetylase and ADP ribose transferase activities.

Year introduced: 2003


SIR2 protein, S cerevisiae [Supplementary Concept]

an NAD-dependent histone deacetylase involved in inhibiting transcription of the silent mating-type loci HML & HMR

Date introduced: July 15, 1994


Sirt1 protein, rat [Supplementary Concept]

RefSeq XM_228146

Date introduced: August 7, 2004


Sirt2 protein, mouse [Supplementary Concept]

RefSeq NM_022432

Date introduced: January 24, 2001


Sirtuin 3

A sirtuin family member found primarily in MITOCHONDRIA. It is a multifunctional enzyme that contains a NAD-dependent deacetylase activity that is specific for HISTONES and a mono-ADP-ribosyltransferase activity.

Year introduced: 2010


Sirtuin 2

A sirtuin family member found primarily in the CYTOPLASM. It is a multifunctional enzyme that contains a NAD-dependent deacetylase activity that is specific for HISTONES and a mono-ADP-ribosyltransferase activity.

Year introduced: 2010


Sirtuin 1

A sirtuin family member found primarily in the CELL NUCLEUS. It is an NAD-dependent deacetylase with specificity towards HISTONES and a variety of proteins involved in gene regulation.

Year introduced: 2010


Fibrinogens, Abnormal

Fibrinogens which have a functional defect as the result of one or more amino acid substitutions in the amino acid sequence of normal fibrinogen. Abnormalities of the fibrinogen molecule may impair any of the major steps involved in the conversion of fibrinogen into stabilized fibrin, such as cleavage of the fibrinopeptides by thrombin, polymerization and cross-linking of fibrin. The resulting dysfibrinogenemias can be clinically silent or can be associated with bleeding, thrombosis or defective wound healing.

Year introduced: 1989


West Nile virus

A species of FLAVIVIRUS, one of the Japanese encephalitis virus group (ENCEPHALITIS VIRUSES, JAPANESE). It can infect birds and mammals. In humans, it is seen most frequently in Africa, Asia, and Europe presenting as a silent infection or undifferentiated fever (WEST NILE FEVER). The virus appeared in North America for the first time in 1999. It is transmitted mainly by CULEX spp mosquitoes which feed primarily on birds, but it can also be carried by the Asian Tiger mosquito, AEDES albopictus, which feeds mainly on mammals.

Year introduced: 1973 (1965)



A disturbance in the normal fluency and time patterning of speech that is inappropriate for the individual's age. This disturbance is characterized by frequent repetitions or prolongations of sounds or syllables. Various other types of speech dysfluencies may also be involved including interjections, broken words, audible or silent blocking, circumlocutions, words produced with an excess of physical tension, and monosyllabic whole word repetitions. Stuttering may occur as a developmental condition in childhood or as an acquired disorder which may be associated with BRAIN INFARCTIONS and other BRAIN DISEASES. (From DSM-IV, 1994)


Lymphocytic choriomeningitis virus

The type species of ARENAVIRUS, part of the Old World Arenaviruses (ARENAVIRUSES, OLD WORLD), producing a silent infection in house and laboratory mice. In humans, infection with LCMV can be inapparent, or can present with an influenza-like illness, a benign aseptic meningitis, or a severe meningoencephalomyelitis. The virus can also infect monkeys, dogs, field mice, guinea pigs, and hamsters, the latter an epidemiologically important host.

Year introduced: 1973(1965)



A family of RNA viruses naturally infecting rodents and consisting of one genus (ARENAVIRUS) with two groups: Old World Arenaviruses (ARENAVIRUSES, OLD WORLD) and New World Arenaviruses (ARENAVIRUSES, NEW WORLD). Infection in rodents is persistent and silent. Vertical transmission is through milk-, saliva-, or urine-borne routes. Horizontal transmission to humans, monkeys, and other animals is important.

Year introduced: 1981


Akinetic Mutism

A syndrome characterized by a silent and inert state without voluntary motor activity despite preserved sensorimotor pathways and vigilance. Bilateral FRONTAL LOBE dysfunction involving the anterior cingulate gyrus and related brain injuries are associated with this condition. This may result in impaired abilities to communicate and initiate motor activities. (From Adams et al., Principles of Neurology, 6th ed, p348; Fortschr Neurol Psychiatr 1995 Feb;63(2):59-67)

Year introduced: 1971


Familial cerebral cavernous malformation [Supplementary Concept]

Hereditary autosomal dominant cavernous hemangiomas of the central nervous system that are distinct from INTRACRANIAL ARTERIOVENOUS MALFORMATIONS and are angiographically silent. The hemangiomas are benign, highly proliferative lesions involving aberrant localized growth of CAPILLARY ENDOTHELIUM and develop shortly after birth. Mutations in the KRIT1 (CCM1) gene have been identified. OMIM: 116860

Date introduced: August 25, 2010


SIRT6 protein, human [Supplementary Concept]

RefSeq NM_016539

Date introduced: January 30, 2007


SIRT4 protein, mouse [Supplementary Concept]

RefSeq XM_485674

Date introduced: November 15, 2006

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