Structure and Evolution of APOBEC3-Vif Interactions

限制因子是先天免疫系统的一个分支，可以有效地抑制病毒复制。一批 病毒病原体编码可以对抗限制因子的辅助蛋白，这使得病毒 在宿主中传播。随着进化时间的推移，限制因子进化以逃避病毒拮抗剂，从而限制 病毒的宿主范围。反过来，病毒可以适应这些变化，并通过快速跨物种进入新的宿主 辅助蛋白的进化。灵长类APOBEC3胞苷脱氨酶可以说是最 广泛研究了家族的制约因素。它们通过以下方式阻止逆转录病毒和逆转录病毒的传播 使它们的基因组发生高度突变，并有可能抑制艾滋病病毒HIV-1。然而，HIV-1 辅助蛋白Vif通过靶向宿主降解APOBEC3酶来有效抑制APOBEC3酶 泛素-蛋白酶体系统。VIF在所有现有的慢病毒中都是保守的，包括那些起源于灵长类的慢病毒 作为SIV。在VIF中的适应允许SIV从猴子到黑猩猩的跨物种传播 这是HIV-1的古老起源的基础。因此，APOBEC3-VIF交互是一个典型的 限制因子和病毒拮抗剂。原则上，通过APOBEC3突变和病毒适应宿主逃逸 VIF可以通过改变蛋白质结合界面，插入短线状相互作用基序 基因丢失和变构位点的叠印或突变。然而，没有Vif的共结构被约束到 任何APOBEC3家族成员都记录了这些现象，因此详细的机制尚不清楚。在这 项目中，我们将覆盖在关键时间点积累的测序和病毒传染性数据 HIV-1的进化历史和相应的Vif-A3复合体的结构。尖端方法，如 作为FAB辅助的单粒子低温EM，将被用来解析这些结构。的功能意义 观察到的相互作用将通过突变结合细胞和病毒感染性分析进行测试。 体外泛素化活性测定。这个项目将提供一个生物化学的范例， 寄主-病原菌的普遍现象--分子军备竞赛的结构和分子机制 互动。

Restriction factors are a branch of the innate immune system that potently inhibit viral replication. A number of viral pathogens encode accessory proteins that can antagonize restriction factors, which allows viral dissemination in host. Over evolutionary time, restriction factors evolve to escape viral antagonists, limiting the host range of viruses. In turn, viruses can adapt to these changes and cross species into new hosts by rapid evolution of accessory proteins. The primate APOBEC3 cytidine deaminases are arguably the most extensively studied family of restriction factors. They block the spread of retroviruses and retroelements by hypermutating their genomes and have the potential to inhibit the AIDS virus, HIV-1. However, the HIV-1 accessory protein Vif potently suppresses APOBEC3 enzymes by targeting them for degradation by the host ubiquitin-proteasome system. Vif is conserved in all existing lentiviruses, including those of primate origin such as SIV. Adaptation in Vif has allowed cross-species transmission of SIV from monkeys to chimpanzees and underlies the ancient origin of HIV-1. Accordingly, the APOBEC3-Vif interaction is an archetypical case of a restriction factor and viral antagonist. In principle, host escape by mutation in APOBEC3 and viral adaptation in Vif could occur through changes in protein binding interfaces, insertion of short-linear interaction motifs by gene loss and overprinting or mutation of allosteric sites. However, there are no co-structures of Vif bound to any APOBEC3 family member to document these phenomena, so the detailed mechanisms are unclear. In this project, we will overlay sequencing and viral infectivity data accumulated at critical points during the evolutionary history of HIV-1 with structures of corresponding Vif-A3 complexes. Cutting edge methods, such as Fab-assisted single-particle cryo-EM, will be used to resolve these structures. The functional significance of the observed interactions will be tested by mutagenesis in conjunction with viral infectivity assays in cells and Vif ubiquitination activity assays in vitro. This project will provide a paradigmatic example of the biochemistry, structure, and molecular mechanisms of molecular arms races that are general phenomena of host-pathogen interactions.