HIV-1 evolution driven by intracellular defenses

逆转录病毒已经设计了许多策略来逃避旨在预防逆转录病毒感染的细胞机制。 HIV-1表达Vif，一种抵消胞苷脱氨酶APOBEC 3G和APOBEC 3F的抗病毒活性的蛋白质。 然而，HIV-1基因组的核苷酸组成表明， 脱氨基作用可能不是绝对的。在初步研究中，我们发现vif基因编码的蛋白质不能降解 可以在体内检测APOBEC 3G、APOBEC 3F或两者。Vif功能的缺失定位于单核苷酸 替代品这些研究表明，Vif功能的自然变异可能会深刻影响细胞凋亡的程度和方向。 HIV-1感染者体内的病毒序列进化。 本文提出的实验将确定宿主机制旨在防止逆转录病毒的程度 事实上，感染有助于病毒多样化和致病性。我们将分析表达Vif的病毒的适应性 与APOBEC 3G或APOBEC 3F活性密切相关但在中和APOBEC 3G或APOBEC 3F活性的能力上不同的蛋白质。我们还将测试 Vif功能的变化在某些情况下可能有利于病毒适应（例如，存在下 通过确定APOBEC 3G或APOBEC 3F对胞苷脱氨基作用是否选择某些药物 耐药突变与胞苷脱氨基作用的部分保护相关的超突变模式将是 与艾滋病病毒适应性相关由于APOBEC 3酶在不同的二核苷酸背景下诱导超突变， 了解如何维持对一种酶而不是另一种酶的活性与病毒进化有关。我们将 进行结构功能研究以确定Vif SOCS盒基序以外的结构域是否是必需的， 对于Vif介导的APOBEC 3酶的特异性中和是必需的。最后，我们将评估逆转的影响。 转录和APOBECS驱动的突变对Vif功能丧失的影响。我们将确定Vif失活率， 逆转录酶或胞苷脱氨基诱导的突变在单细胞水平上的结果，使用基于 荧光标记的APOBEC 3G降解。Vif功能的变化可能通过使HIV-1的致病性降低而影响HIV-1的致病性。 其基因组或多或少地抵抗脱氨酶活性，这些研究有可能揭示Vif如何介导 胞苷脱氨基保护在体内被调节。

Retroviruses have devised a number of strategies to evade cellular mechanisms aimed at preventing retroviral infection. HIV-1 expressesVif, a protein that counteracts the antiviral activity of the cytidine deaminases APOBEC3G and APOBEC3F. The nucleotide composition of the HIV-1 genome suggests, however, that protection from host-mediated viral cDNA deamination may not be absolute. In preliminary studies, we showed that vif genes encoding proteins that fail to degrade APOBEC3G, APOBEC3F or both can be detected in vivo. The loss of Vif function was mapped to single nucleotide substitutions. These studies indicate that natural variation in Vif function may profoundly impact the extent and direction of viral sequence evolution within HIV-1 infected individuals. The experiments proposed herein will determine the extent to which host mechanisms aimed to prevent retroviral infection, in fact, contribute to viral diversification and pathogenesis. We will analyze the fitness of viruses expressing Vif proteins that are closely related but differ in their ability to neutralize APOBEC3G or APOBEC3F activities. We will also test if variation in Vif function may be beneficial for viral adaptation under certain circumstances (e.g., in the presence of antiretroviral drugs) by determining whether cytidine deamination by APOBEC3G or APOBEC3F selects for certain drug resistance mutations. The pattern of hypermutations associated with partial protection from cytidine deamination will be correlated to HIV fitness. Since APOBEC3 enzymes induce hypermutations in different dinucleotide contexts the understanding of how activity against one enzyme but not the other is maintained is relevant for viral evolution. We will conduct structure function studies to determine whether domains other than the Vif SOCS box motif are necessary and essential for Vif mediated specific neutralization of APOBEC3 enzymes. Finally, we will assess the impact of reverse transcription and APOBECS-driven mutagenesis on loss of Vif function. We will determine the rate of Vif inactivation as result of either reverse transcriptase or cytidine deamination induced mutations on a single cell level using assays based on fluorescence tagged APOBEC3G degradation. Variation in Vif function may influence the pathogenicity of HIV-1 by rendering its genome more or less resistant to deaminase activity and these studies have the potential to reveal how Vif mediated protection from cytidine deamination is modulated in vivo.