Restrictive influence of SAMHD1 on Hepatitis B Virus life cycle

Abstract

Deoxynucleotide triphosphates (dNTPs) are essential for efficient hepatitis B virus (HBV) replication. Here, we investigated the influence of the restriction factor SAMHD1, a dNTP hydrolase (dNTPase) and RNase, on HBV replication. We demonstrated that silencing of SAMHD1 in hepatic cells increased HBV replication, while overexpression had the opposite effect. SAMHD1 significantly affected the levels of extracellular viral DNA as well as intracellular reverse transcription products, without affecting HBV RNAs or cccDNA. SAMHD1 mutations that interfere with the dNTPase activity (D137N) or in the catalytic center of the histidine-aspartate (HD) domain (D311A), and a phospho-mimetic mutation (T592E), abrogated the inhibitory activity. In contrast, a mutation diminishing the potential RNase but not dNTPase activity (Q548A) and a mutation disabling phosphorylation (T592A) did not affect antiviral activity. Moreover, HBV restriction by SAMHD1 was rescued by addition of deoxynucleosides. Although HBV infection did not directly affect protein level or phosphorylation of SAMHD1, the virus upregulated intracellular dATPs. Interestingly, SAMHD1 was dephosphorylated, thus in a potentially antiviral-active state, in primary human hepatocytes. Furthermore, SAMHD1 was upregulated by type I and II interferons in hepatic cells. These results suggest that SAMHD1 is a relevant restriction factor for HBV and restricts reverse transcription through its dNTPase activity.

Cyclin E2‐CDK2 mediates SAMHD1 phosphorylation to abrogate its restriction of HBV replication in hepatoma cells

“…Wild-type SAMDH1 and its T592V mutant that cannot be phosphorylated both still inhibited HBV replication, while this antiviral function was lost for the dNTPase-deficient D207N and D137N mutants and the phosphomimetic mutant T592E in Huh7 cells ( Fig. 1A), which was in accordance with previous reports [19]. These results suggested that the dNTPase activity and an unphosphorylated state of SAMHD1 are both essential for restricting HBV replication.…”

Quantitative Proteomic Approach Identifies Vpr Binding Protein as Novel Host Factor Supporting Influenza A Virus Infections in Human Cells

“…6), raising the question for its mode of action. Our data support a model in which the positive effects of VprBP for cellular and viral gene expression in infected cells are at least partially exerted via degradation of its binding partner SAMHD1, which is known to deplete cellular dNTP levels and to degrade viral RNA (56,58,77). Indeed, we detected decreased SAMHD1 expression levels during permissive Pan infection (Fig.…”

“…VprBP has been described to facilitate proteasomal degradation of SAMHD1, a known restriction factor for several human pathogens including hepatitis B virus, herpes simplex virus, vaccinia virus and retroviruses (52)(53)(54)(55)(56)(57)(58). To investigate the hypothesis that SAMHD1 is regulated in influenza virus infection we compared its expression in human cells infected with the Pan or Mal viruses, respectively, at 4 h and 16 h p.i.…”

Roles of SAMHD1 in antiviral defense, autoimmunity and cancer

“…Additionally, SAMHD1 has been reported to restrict the double‐stranded DNA viruses, vaccinia, and Herpes simplex virus type 1, in nondividing target cells through its dNTP triphosphohydrolase activity . The SAMHD1 inhibited replication of a third DNA virus, hepatitis B virus , in liver cells, which has been further confirmed by 2 recent studies . Moreover, it was reported that porcine SAMHD1 restricts replication of the highly pathogenic porcine reproductive and respiratory syndrome virus, which is a positive‐stranded RNA virus .…”

“…16,17 The SAMHD1 inhibited replication of a third DNA virus, hepatitis B virus , in liver cells, 18 which has been further confirmed by 2 recent studies. 19,20 Moreover, it was reported that porcine SAMHD1 restricts replication of the highly pathogenic porcine reproductive and respiratory syndrome virus, which is a positive-stranded RNA virus. 21 Taken together, these studies indicate that SAMHD1 broadly inhibits replication of retroviruses, DNA viruses or RNA viruses and thus, has broad antiviral activity ( Table 1).…”