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J Virol. 2018 Jul 17;92(15). pii: e00292-18. doi: 10.1128/JVI.00292-18. Print 2018 Aug 1.

SAMHD1 Impairs HIV-1 Gene Expression and Negatively Modulates Reactivation of Viral Latency in CD4+ T Cells.

Author information

1
Center for Retrovirus Research, The Ohio State University, Columbus, Ohio, USA.
2
Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA.
3
Department of Microbiology, The Ohio State University, Columbus, Ohio, USA.
4
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
5
Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA.
6
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, USA.
7
Center for Retrovirus Research, The Ohio State University, Columbus, Ohio, USA wu.840@osu.edu.

Abstract

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) restricts human immunodeficiency virus type 1 (HIV-1) replication in nondividing cells by degrading intracellular deoxynucleoside triphosphates (dNTPs). SAMHD1 is highly expressed in resting CD4+ T cells, which are important for the HIV-1 reservoir and viral latency; however, whether SAMHD1 affects HIV-1 latency is unknown. Recombinant SAMHD1 binds HIV-1 DNA or RNA fragments in vitro, but the function of this binding remains unclear. Here we investigate the effect of SAMHD1 on HIV-1 gene expression and reactivation of viral latency. We found that endogenous SAMHD1 impaired HIV-1 long terminal repeat (LTR) activity in monocytic THP-1 cells and HIV-1 reactivation in latently infected primary CD4+ T cells. Overexpression of wild-type (WT) SAMHD1 suppressed HIV-1 LTR-driven gene expression at a transcriptional level. Tat coexpression abrogated SAMHD1-mediated suppression of HIV-1 LTR-driven luciferase expression. SAMHD1 overexpression also suppressed the LTR activity of human T-cell leukemia virus type 1 (HTLV-1), but not that of murine leukemia virus (MLV), suggesting specific suppression of retroviral LTR-driven gene expression. WT SAMHD1 bound to proviral DNA and impaired reactivation of HIV-1 gene expression in latently infected J-Lat cells. In contrast, a nonphosphorylated mutant (T592A) and a dNTP triphosphohydrolase (dNTPase) inactive mutant (H206D R207N [HD/RN]) of SAMHD1 failed to efficiently suppress HIV-1 LTR-driven gene expression and reactivation of latent virus. Purified recombinant WT SAMHD1, but not the T592A and HD/RN mutants, bound to fragments of the HIV-1 LTR in vitro These findings suggest that SAMHD1-mediated suppression of HIV-1 LTR-driven gene expression potentially regulates viral latency in CD4+ T cells.IMPORTANCE A critical barrier to developing a cure for HIV-1 infection is the long-lived viral reservoir that exists in resting CD4+ T cells, the main targets of HIV-1. The viral reservoir is maintained through a variety of mechanisms, including regulation of the HIV-1 LTR promoter. The host protein SAMHD1 restricts HIV-1 replication in nondividing cells, but its role in HIV-1 latency remains unknown. Here we report a new function of SAMHD1 in regulating HIV-1 latency. We found that SAMHD1 suppressed HIV-1 LTR promoter-driven gene expression and reactivation of viral latency in cell lines and primary CD4+ T cells. Furthermore, SAMHD1 bound to the HIV-1 LTR in vitro and in a latently infected CD4+ T-cell line, suggesting that the binding may negatively modulate reactivation of HIV-1 latency. Our findings indicate a novel role for SAMHD1 in regulating HIV-1 latency, which enhances our understanding of the mechanisms regulating proviral gene expression in CD4+ T cells.

KEYWORDS:

HIV-1; LTR; SAMHD1; gene expression; latency; reactivation

PMID:
29793958
PMCID:
PMC6052313
DOI:
10.1128/JVI.00292-18
[Indexed for MEDLINE]
Free PMC Article

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