The human immunodeficiency virus type 1 Vif protein reduces intracellular expression and inhibits packaging of APOBEC3G (CEM15), a cellular inhibitor of virus infectivity
The human immunodeficiency virus type 1 Vif protein reduces intracellular expression and inhibits packaging of APOBEC3G (CEM15), a cellular inhibitor of virus infectivity
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DOI：
10.1128/jvi.77.21.11398-11407.2003
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发表时间：
2003-11-01
影响因子：
5.4
通讯作者：
Strebel, M
中科院分区：
文献类型：
--
作者：
Kao, S;Khan, MA;Strebel, M
人类免疫缺陷病毒1型（HIV-1）在大多数原代细胞和一些永生化t细胞系中的复制取决于病毒感染因子（Vif）的活性。Vif具有抵抗细胞抑制剂的能力，这种细胞抑制剂最近被鉴定为CEM15，可以阻断Vif缺陷HIV-1变异的传染性。CEM15与APOBEC3G相同，属于参与RNA和DNA脱氨的蛋白质家族。我们从人肾cDNA文库中克隆了APOBEC3G，并证实该蛋白是HIV复制的有效抑制剂，并且对Vif的活性敏感。我们发现野生型Vif以剂量依赖的方式抑制APOBEC3G包装成病毒颗粒。相比之下，在Vif的各个区域携带两个高度保守的半胱氨酸残基突变的框内缺失的生物无活性变体并没有抑制APOBEC3G的包装。有趣的是，APOBEC3G在野生型Vif存在下的表达不仅影响病毒包装，还降低其细胞内表达水平。这种效应在无生物活性的Vif变体中没有观察到。脉冲追踪分析没有发现在Vif存在或不存在时APOBEC3G的稳定性有显著差异。然而，在Vif的存在下，APOBEC3G的合成速度略有降低。Vif存在时细胞内APOBEC3G的减少并不能完全解释Vif诱导的病毒相关APOBEC3G的减少，这表明Vif可能在多个水平上起作用，以防止APOBEC3G被包装成病毒颗粒。
Replication of human immunodeficiency virus type 1 (HIV-1) in most primary cells and some immortalized T-cell lines depends on the activity of the viral infectivity factor (Vif). Vif has the ability to counteract a cellular inhibitor, recently identified as CEM15, that blocks infectivity of Vif-defective HIV-1 variants. CEM15 is identical to APOBEC3G and belongs to a family of proteins involved in RNA and DNA deamination. We cloned APOBEC3G from a human kidney cDNA library and confirmed that the protein acts as a potent inhibitor of HIV replication and is sensitive to the activity of Vif. We found that wild-type Vif inhibits packaging of APOBEC3G into virus particles in a dose-dependent manner. In contrast, biologically inactive variants carrying in-frame deletions in various regions of Vif or mutation of two highly conserved cysteine residues did not inhibit packaging of APOBEC3G. Interestingly, expression of APOBEC3G in the presence of wild-type Vif not only affected viral packaging but also reduced its intracellular expression level. This effect was not seen in the presence of biologically inactive Vif variants. Pulse-chase analyses did not reveal a significant difference in the stability of APOBEC3G in the presence or absence of Vif. However, in the presence of Vif, the rate of synthesis of APOBEC3G was slightly reduced. The reduction of intracellular APOBEC3G in the presence of Vif does not fully account for the Vif-induced reduction of virus-associated APOBEC3G, suggesting that Vif may function at several levels to prevent packaging of APOBEC3G into virus particles.