National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun 130012, China; The First Hospital and Institute of Immunology, Jilin University, Changchun 130012, China.
National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun 130012, China.
J Biol Chem. 2020 Mar 27;295(13):4252-4264. doi: 10.1074/jbc.RA120.012767. Epub 2020 Feb 19.
SAM and HD domain-containing protein 1 (SAMHD1) is a host factor that restricts reverse transcription of lentiviruses such as HIV in myeloid cells and resting T cells through its dNTP triphosphohydrolase (dNTPase) activity. Lentiviruses counteract this restriction by expressing the accessory protein Vpx or Vpr, which targets SAMHD1 for proteasomal degradation. SAMHD1 is conserved among mammals, and the feline and bovine SAMHD1 proteins (fSAM and bSAM) restrict lentiviruses by reducing cellular dNTP concentrations. However, the functional regions of fSAM and bSAM that are required for their biological functions are not well-characterized. Here, to establish alternative models to investigate SAMHD1 , we studied the restriction profile of fSAM and bSAM against different primate lentiviruses. We found that both fSAM and bSAM strongly restrict primate lentiviruses and that Vpx induces the proteasomal degradation of both fSAM and bSAM. Further investigation identified one and five amino acid sites in the C-terminal domain (CTD) of fSAM and bSAM, respectively, that are required for Vpx-mediated degradation. We also found that the CTD of bSAM is directly involved in mediating bSAM's antiviral activity by regulating dNTPase activity, whereas the CTD of fSAM is not. Our results suggest that the CTDs of fSAM and bSAM have important roles in their antiviral functions. These findings advance our understanding of the mechanism of fSAM- and bSAM-mediated viral restriction and might inform strategies for improving HIV animal models.
SAM 和富含 HD 结构域蛋白 1（SAMHD1）是一种宿主因子，通过其 dNTP 三磷酸水解酶（dNTPase）活性限制逆转录病毒（如 HIV）在髓系细胞和静止 T 细胞中的逆转录。逆转录病毒通过表达辅助蛋白 Vpx 或 Vpr 来拮抗这种限制，Vpx 或 Vpr 将 SAMHD1 靶向蛋白酶体降解。SAMHD1 在哺乳动物中保守，猫和牛的 SAMHD1 蛋白（fSAM 和 bSAM）通过降低细胞内 dNTP 浓度来限制逆转录病毒。然而，fSAM 和 bSAM 发挥其生物学功能所需的功能区域尚未得到很好的描述。在这里，为了建立替代模型来研究 SAMHD1，我们研究了 fSAM 和 bSAM 对不同灵长类逆转录病毒的限制谱。我们发现 fSAM 和 bSAM 都强烈限制灵长类逆转录病毒，并且 Vpx 诱导 fSAM 和 bSAM 的蛋白酶体降解。进一步的研究确定了 fSAM 和 bSAM 的 C 末端结构域（CTD）中的一个和五个氨基酸位点分别是 Vpx 介导降解所必需的。我们还发现 bSAM 的 CTD 通过调节 dNTPase 活性直接参与介导 bSAM 的抗病毒活性，而 fSAM 的 CTD 则没有。我们的结果表明，fSAM 和 bSAM 的 CTD 在它们的抗病毒功能中起着重要作用。这些发现加深了我们对 fSAM 和 bSAM 介导的病毒限制机制的理解，并可能为改善 HIV 动物模型的策略提供信息。
