Role of APOBEC3 in in vivo Restriction of Retrovirus Infection

 描述（由申请人提供）：在整个进化过程中，感染性病原体已感染原核生物和真核生物。事实上，在生物体和它们的感染因子之间存在着共同进化，宿主会产生保护性反应，而感染因子则会对它们采取适应性对策。一种病毒限制系统由载脂蛋白B编辑复合物3（A3）蛋白质家族赋予，其使单链DNA中的脱氧胞苷残基脱氨基，导致GC至AT转变。A3基因在拷贝数和序列方面都具有高度多态性，并显示出强有力的正选择证据，表明它们是在响应病毒等感染因子而进化的。逆转录病毒和其它病毒显示脱氨基足迹，表明它们又处于A3蛋白的选择压力下，并且已经表明A3介导的病毒DNA的脱氨基可以导致药物-抵抗和免疫逃逸变体。虽然已经了解了很多关于A3蛋白及其在病毒限制中的作用，但大多数研究是在培养的细胞中进行的，通常使用过表达的蛋白质和从患者组织分离的病毒的序列分析，或者在人原代细胞中的实验由于7种人A3基因的存在而复杂化，其中许多基因在相同的细胞类型中表达。事实上，尽管A3 B、A3 D、A3 F、A3 G和A3 H在过表达时都限制HIV和其他病毒，但它们在体内控制感染中的作用仍不清楚。我们的实验室率先使用体内小鼠模型来研究A3蛋白如何限制逆转录病毒的感染。我们已经开发了基因敲除小鼠和最近的基因工程动物，表达个别人A3蛋白，以研究小鼠乳腺肿瘤病毒和小鼠白血病病毒的感染。在这里，我们建议使用这些小鼠模型来研究单个人A3蛋白如何发挥作用以限制体内感染，塑造病毒进化并影响免疫逃逸和耐药逆转录病毒的发展。因此，这些研究将增加我们对A3蛋白体内作用机制的理解，并为测试抗病毒药物治疗提供模型。

 DESCRIPTION (provided by applicant): Infectious agents have infected prokaryotes and eukaryotes throughout evolution. Indeed, there is co-evolution among organisms and their infectious agents, with development of protective responses in the hosts and adaptive countermeasures to them by the infectious agents. One system of viral restriction is conferred by the Apolipoprotein B editing complex 3 (A3) family of proteins, which deaminate deoxycytidine residues in single-stranded DNA leading to GC-to-AT transitions. A3 genes are highly polymorphic both with regard to copy number and sequence and show strong evidence of positive selection, indicating that they are evolving in response to infectious agents like viruses Similarly, retroviruses and other viruses show deamination footprints suggesting they in turn are under selective pressure by A3 proteins and it has been suggested that A3-mediated deamination of viral DNA could lead to both drug-resistant and immune escape variants. While much has been learned about A3 proteins and their roles in virus restriction, most studies have been carried out in cultured cells, often using over- expressed proteins and sequence analysis of viruses isolated from patient tissue or experiments in human primary cells are complicated by the presence of 7 human A3 genes, many of which are expressed in the same cell types. Indeed while A3B, A3D, A3F, A3G and A3H all restrict HIV and other viruses when over-expressed, there role in control of infection in vivo remains unclear. Our lab pioneered the use of in vivo mouse models to study how A3 proteins restrict infection by retroviruses. We have developed knockout mice and more recently genetically engineered animals that express individual human A3 proteins to study infection by mouse mammary tumor virus and murine leukemia virus. Here, we propose to use these mouse models to study how individual human A3 proteins function in to restrict in vivo infection, shape virus evolution and affect the developmen of immune escape and drug-resistant retroviruses. These studies will thus add to our understanding of A3 proteins mechanism of action in vivo as well as provide models for testing anti-viral drug therapies.