High level expression of human immunodeficiency virus type-1 Vif inhibits viral infectivity by modulating proteolytic processing of the gag precursor at the p2/nucleocapsid processing site
High level expression of human immunodeficiency virus type-1 Vif inhibits viral infectivity by modulating proteolytic processing of the gag precursor at the p2/nucleocapsid processing site
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DOI：
10.1074/jbc.m312426200
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发表时间：
2004-03-26
影响因子：
4.8
通讯作者：
Strebel, K
中科院分区：
文献类型：
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作者：
Akari, H;Fujita, M;Strebel, K
人类免疫缺陷病毒 1 型 Vif 蛋白在调节病毒感染性方面发挥着至关重要的作用。然而，我们发现新合成的 Vif 会被细胞蛋白酶迅速降解。我们在不允许的 H9 细胞中测试了 Vif 的剂量依赖性，发现 Vif 在低水平表达时，以剂量依赖性方式增加病毒感染性。然而，令人惊讶的是，最佳病毒感染性所需的 Vif 范围很窄，Vif 的进一步增加会严重降低病毒感染性。高水平 Vif 对病毒感染性的抑制与细胞类型无关，并且与 Gag 加工中间体的积累有关。 Vif 不充当一般蛋白酶抑制剂，而是选择性抑制衣壳和核衣壳 (NC) 边界的 Gag 加工。对有效包装但无法调节 Gag 加工的 Vif 变体的鉴定表明，Vif 包装对于 33-和 34-kDa 加工中间体的生产是必要的，但还不够。有趣的是，这些加工中间体，如 Vif，与病毒核蛋白复合物的结合比成熟衣壳和 NC 更紧密。我们得出结论，病毒相关的 Vif 抑制 p2/NC 初级切割位点的 Gag 前体分子子集的加工。 Vif 生理水平对一小部分 Gag 分子加工的调节可能对病毒成熟很重要。然而，此类加工中间体在高水平 Vif 下的积累具有抑制作用。因此，Vif 的快速细胞内降解可能已发展成为防止 Vif 的此类抑制作用的机制。
The human immunodeficiency virus type-1 Vif protein has a crucial role in regulating viral infectivity. However, we found that newly synthesized Vif is rapidly degraded by cellular proteases. We tested the dose dependence of Vif in non-permissive H9 cells and found that Vif, when expressed at low levels, increased virus infectivity in a dose-dependent manner. Surprisingly, however, the range of Vif required for optimal virus infectivity was narrow, and further increases in Vif severely reduced viral infectivity. Inhibition of viral infectivity at higher levels of Vif was cell type-independent and was associated with an accumulation of Gag-processing intermediates. Vif did not act as a general protease inhibitor but selectively inhibited Gag processing at the capsid and nucleocapsid (NC) boundary. Identification of Vif variants that were efficiently packaged but were unable to modulate Gag processing suggests that Vif packaging was necessary but insufficient for the production of 33- and 34-kDa processing intermediates. Interestingly, these processing intermediates, like Vif, associated with viral nucleoprotein complexes more rigidly than mature capsid and NC. We conclude that virus-associated Vif inhibits processing of a subset of Gag precursor molecules at the p2/NC primary cleavage site. Modulation of processing of a small subset of Gag molecules by physiological levels of Vif may be important for virus maturation. However, the accumulation of such processing intermediates at high levels of Vif is inhibitory. Thus, rapid intracellular degradation of Vif may have evolved as a mechanism to prevent such inhibitory effects of Vif.