HIV-1 evolution driven by intracellular defenses

逆转录病毒已经设计了一些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，这是一种蛋白质，可以抵消胞苷脱氨酶APOBEC3G和APOBEC3F的抗病毒活性。 然而，HIV-1基因组的核苷酸组成表明，对宿主介导的病毒c DNA的保护 去氨基可能不是绝对的。在初步研究中，我们发现vif基因编码不能降解的蛋白质。 在体内可以检测到APOBEC3G和/或APOBEC3F。Vif功能缺失被映射到单核苷酸 替换。这些研究表明，VIF功能的自然变异可能会深刻地影响VIF功能的程度和方向 HIV-1感染者体内的病毒序列进化。 这里提出的实验将确定宿主机制在多大程度上旨在预防逆转录病毒 事实上，感染有助于病毒的多样化和致病。我们将分析表达Vif的病毒的适合性 密切相关但中和APOBEC3G或APOBEC3F活性的能力不同的蛋白质。我们还将测试是否 Vif功能的变化在某些情况下可能有利于病毒适应(例如，在存在 抗逆转录病毒药物)，通过确定APOBEC3G或APOBEC3F对胞苷脱氨基是否选择特定药物 抗药性突变。与胞苷脱氨基的部分保护相关的超突变模式将是 与艾滋病毒的健康状况有关。由于APOBEC3酶在不同的二核苷酸环境中诱导超突变， 了解针对一种酶而不是另一种酶的活性是如何保持的，这与病毒进化有关。我们会 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要的 对Vif介导的APOBEC3酶的特异性中和至关重要。最后，我们将评估反转的影响 转录和APOBECs驱动的Vif功能丧失的突变。我们将VIF的失活率确定为 逆转录酶或胞苷脱氨诱导单细胞水平突变的结果 荧光标记APOBEC3G降解。Vif功能的变异可能通过呈现影响HIV-1的致病性 它的基因组或多或少对脱氨酶活性有抵抗力，这些研究有可能揭示Vif是如何 对胞苷脱氨的保护作用是在体内调节的。

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.