Structure of the Retroviral Restriction Factor, TRIM5alpha

描述（由申请人提供）：灵长类动物表达在病毒进入宿主细胞后不久但在逆转录之前阻断某些逆转录病毒感染的显性限制因子。逆转录病毒衣壳是限制易感性的决定因素。TRIM5a或在某些物种中，TRIMCyp介导灵长类细胞对逆转录病毒感染的阻断。TRIM5a是tripartite motif （TRIM）蛋白家族的成员，包含RING、B-box 2和coil -coil结构域。TRIM5a还含有一个羧基末端B30.2/SPRY结构域，该结构域已被证明有助于衣壳识别。不同灵长类动物TRIM5a蛋白的B30.2/SPRY结构域的差异解释了观察到的逆转录病毒限制模式。例如，导致获得性免疫缺陷综合征（AIDS）的人类免疫缺陷病毒（HIV-1）受到来自旧大陆猴的TRIM5a蛋白的有效抑制，但仅受到人类TRIM5a的适度抑制。人类TRIM5a B30.2结构域可变区域内的单个精氨酸残基降低了对HIV-1衣壳的亲和力，导致限制性减弱。了解TRIM5a衣壳识别的结构基础，可能会提出增强这种逆转录病毒的先天细胞内免疫的方法。这项工作的总体目标是了解灵长类TRIM5a和TRIMCyp蛋白的结构，并研究它们与组装的逆转录病毒衣壳的相互作用。本研究的具体目的是：1)建立和优化灵长类动物TRIM5a和TRIMCyp蛋白的表达系统；2)构建适合于结构分析的TRIM5a和TRIMCyp片段；3)鉴定和表征TRIM5a促进结晶的配体。人类免疫缺陷病毒（HIV）不能感染猴子，因为这些动物产生一种叫做TRIM5alpha的抵抗因子。人类TRIM5alpha仅能适度阻断HIV。拟议的工作将试图获得TRIM5alpha的详细图像，以便提高其抗hiv活性。

DESCRIPTION (provided by applicant): Primates express dominant restriction factors that block the infection of certain retroviruses soon after the virus enters the host cell but prior to reverse transcription. The retroviral capsid is the determinant of susceptibility to restriction. TRIM5a or, in some species, TRIMCyp mediates the earl blocks to retroviral infection in primate cells. TRIM5a is a member of the tripartite motif (TRIM) family of proteins and contains RING, B-box 2 and coiled-coil domains. TRIM5a also contains a carboxy-terminal B30.2/SPRY domain, which has been shown to contribute to capsid recognition. Differences among the B30.2/SPRY domains of TRIM5a proteins from different primate species account for the observed patterns of retroviral restriction. For example, human immunodeficiency virus (HIV-1), the cause of acquired immunodeficiency syndrome (AIDS), is potently restricted by the TRIM5a protein from Old World monkeys, but only modestly inhibited by human TRIM5a. A single arginine residue within a variable region of the human TRIM5a B30.2 domain decreases the affinity for the HIV-1 capsid, resulting in a diminution of restriction. An understanding of the structural basis of capsid recognition by TRIM5a may suggestion approaches to potentiate this innate intracellular immunity to retroviruses. The overall goal of the work proposed is to understand the structure of primate TRIM5a and TRIMCyp proteins and to investigate their interaction with the assembled retroviral capsid. The specific aims of this proposed are: 1) To establish and optimize systems for the expression of primate TRIM5a and TRIMCyp proteins; 2) To create TRIM5a and TRIMCyp fragments that are suitable for structural analysis; 3) To identify and characterize ligands for TRIM5a that could promote crystallization. Human immunodeficiency virus (HIV) cannot infect monkeys because these animals make a resistance factor called TRIM5alpha. Human TRIM5alpha only modestly blocks HIV. The proposed work will attempt to obtain a detailed picture of TRIM5alpha so that its anti-HIV activity could be improved.