The Role of Vpr and Vpx in Lentivirus Replication

描述（由申请人提供）：HIV-1和其他慢病毒编码辅助蛋白，每种蛋白在促进病毒复制和引起发病中发挥作用。几种辅助蛋白通过对抗抗病毒细胞蛋白发挥作用。这 该项目的重点是了解两种与艾滋病毒相关的辅助蛋白Vpr和Vpx如何促进病毒复制。这些蛋白质在氨基酸序列上50%相似，包装在病毒体中，定位于细胞核并结合特异性E3泛素连接酶。Vpx， 在HIV-2和SIVmac中编码，但在HIV-1中不编码，靶向细胞酶SAMHD 1降解。Vpr的目标尚未确定。SAMHD 1抑制病毒的机制尚不清楚。它是一种磷酸水解酶，当在骨髓细胞中表达时，从脱氧核苷酸三磷酸中去除磷酸盐，消耗细胞内dNTP库。SAMHD 1也是一种外切核酸酶，这些活性中的哪一种限制病毒复制尚不清楚。SAMHD 1不阻断SIVmac或HIV-2的复制，因为这些病毒编码Vpx。该项目旨在了解（i）SAMHD 1限制HIV-1的机制;（ii）Vpx如何结合并靶向SAMHD 1进行降解;（iii）Vpx如何在感染后从病毒中释放;（iv）蛋白质的酶活性如何通过翻译后修饰或通过与调节蛋白质结合来调节;（v） Vpx和SAMHD 1的氨基酸残基允许蛋白质相互作用;（vi）Vpx如何输入细胞核和（vii）SAMHD 1在对HIV-1感染的先天免疫应答中的作用。最后，建立Vpr的诱导表达系统以鉴定靶宿主因子。这些发现将揭示先天免疫系统限制HIV-1和其他人类病原体的新机制，以及病毒如何进化以逃避限制。了解这一点可以提供治疗策略，以增强先天免疫反应治疗感染性疾病的有效性。

DESCRIPTION (provided by applicant): HIV-1 and other lentiviruses encode accessory proteins, each of which plays a role in facilitating virus replication and causing pathogenesis. Several of the accessory proteins exert their effect by counteracting antiviral cell proteins. This project focuses on understanding how the two HIV-related accessory proteins, Vpr and Vpx, facilitate virus replication. These proteins are 50% similar in amino acid sequence, are packaged in the virion, localize to the nucleus and bind a specific E3 ubiquitin ligase. Vpx, which is encoded in HIV-2 and SIVmac but not HIV-1, targets the cellular enzyme SAMHD1 for degradation. The target of Vpr has not yet been identified. The mechanism by which SAMHD1 inhibits viruses is not clear. It is a phosphohydrolase that when expressed in myeloid cells, removes the phosphates from the deoxynucleotide triphosphates, depleting the pool of intracellular dNTPs. SAMHD1 is also an exonuclease and which of these activities restricts virus replication is not clear. SAMHD1 does not block the replication of SIVmac or HIV-2 as these viruses encode Vpx. This project seeks to understand (i) the mechanism by which SAMHD1 restricts HIV-1; (ii) how Vpx binds and targets SAMHD1 for degradation; (iii) how Vpx is released from the virus following infection; (iv) how the enzymatic activity of the protein is regulated by post-translational modifications or by associating with regulatory proteins; (v) which amino acid residues of Vpx and SAMHD1 allow the proteins to interact; (vi) how Vpx is imported into the nucleus and (vii) the role of SAMHD1 in the innate immune response to HIV-1 infection. Lastly, an inducible expression system for Vpr will be established to identify the targeted host factor. The findings will shed light on a new mechanism by which the innate immune system restricts HIV-1 and other human pathogens and how viruses have evolved to escape the restriction. Understanding this may provide strategies to therapeutically enhance the effectiveness of the innate immune response for the treatment of infectious diseases.