Laboratory of Molecular Human Retrovirology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
J Mol Biol. 2013 Aug 23;425(16):2840-52. doi: 10.1016/j.jmb.2013.05.015. Epub 2013 May 23.
The human immunodeficiency virus type 1 (HIV-1) Vif protein counteracts the antiviral activity of the apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3 (APOBEC3) family of proteins by targeting the proteins for degradation through the ubiquitin-proteasome pathway. Previous mutagenic studies have shown that multiple domains of Vif are required for interacting with APOBEC3G proteins and the proteasome pathway. However, very few mutagenesis and functional analyses of patient-derived Vif proteins have been conducted. In this study, we amplified and cloned the HIV-1 vif genes from the peripheral blood mononuclear cells (PBMCs) of five HIV-1-infected individuals in Nairobi and further tested the impact of the genes on anti-A3G activity and HIV-1 replication. The gene sequence analysis revealed high genetic variation of vif genes from different HIV-1-infected individuals. Interestingly, the Vif proteins derived from two of the three long-term survivors (LTSs) displayed a significantly impaired ability to mediate the degradation of A3G. In particular, a single amino acid change (I107T) in one of the non-functional LTS Vif variants, which has not been previously identified in the Los Alamos databases of vif sequences, was found to be responsible for the lack of anti-A3G activity. Further study demonstrated that HIV-1 carrying an I107T Vif mutation displayed significantly reduced fitness in A3G(+) T cells and PBMCs. Moreover, co-infecting A3G(+) T cells with both the wild-type and I107T Vif viruses resulted in decreased viral replication. Overall, the results of this study indicate that the HIV-1 Vif residue I107 is important for its anti-APOBEC3G activity and viral replication, which may have implications for viral fitness in vivo.
人类免疫缺陷病毒 1 型（HIV-1）的 Vif 蛋白通过泛素-蛋白酶体途径将 APOBEC3 家族的蛋白靶向降解，从而拮抗该家族蛋白的抗病毒活性。先前的诱变研究表明，Vif 蛋白的多个结构域都需要与 APOBEC3G 蛋白和蛋白酶体途径相互作用。然而，对来源于患者的 Vif 蛋白进行的诱变和功能分析却很少。在本研究中，我们从内罗毕 5 名 HIV-1 感染者的外周血单核细胞（PBMC）中扩增并克隆了 HIV-1 vif 基因，并进一步检测了这些基因对 A3G 抑制活性和 HIV-1 复制的影响。基因序列分析显示，不同 HIV-1 感染者的 vif 基因存在高度的遗传变异。有趣的是，来自 3 名长期存活者（LTS）中的 2 名的 Vif 蛋白显示出明显降低的介导 A3G 降解的能力。特别是，在一个无功能 LTS Vif 变体中，一个之前在 Los Alamos vif 序列数据库中未被发现的单一氨基酸变化（I107T）被发现是缺乏抗 A3G 活性的原因。进一步的研究表明，携带 I107T Vif 突变的 HIV-1 在 A3G(+)T 细胞和 PBMC 中的适应性显著降低。此外，同时感染 A3G(+)T 细胞的野生型和 I107T Vif 病毒会导致病毒复制减少。总的来说，本研究结果表明，HIV-1 Vif 残基 I107 对其抗 APOBEC3G 活性和病毒复制很重要，这可能对病毒在体内的适应性有影响。
