Regulation of HIV-1 by Rad51 in CNS cells

描述（由申请人提供）：HIV-1中枢神经系统感染可触发一系列防御机制，旨在阻断病毒基因组在其生命周期的各个阶段的表达。反过来，HIV-1通过其附属蛋白进化出了几个调节事件，更值得注意的是Tat，以克服细胞防御途径，并通过一系列不同的调节事件诱导对细胞的最大损伤，同时确保受感染细胞中的多产病毒生命周期。最近，人们越来越关注HIV-1感染对宿主细胞稳态的影响，更具体地说，HIV-1与通过同源和非同源DNA修复控制染色体完整性的细胞途径的相互作用。虽然HIV-1 Vpr在影响DNA损伤中的作用已被充分记录，但最近的观察（如图所示）指出Tat在诱导原代小胶质细胞和星形胶质细胞中Rad51表达的能力，这两种细胞类型在艾滋病的神经发病机制中起着重要作用。这一观察结果证实了感染研究的结果，即在培养的HIV-1感染的小胶质细胞和星形胶质细胞以及患有HIV脑炎的艾滋病大脑中，Rad51水平升高。Rad51是同源重组修复途径的主要调节因子，与其他细胞蛋白协同确保染色体的完整性。显然，Rad51的非预定激活可能会对几种细胞通路产生不利影响，在某些情况下甚至会损害染色体的完整性。有趣的是，Tat蛋白诱导Rad51可能对小胶质细胞和星形胶质细胞中HIV-1启动子活性有正反馈作用。在这方面，我们的初步数据表明，Rad51可能会募集NF-B和cyclin T1，这两种HIV-1的调节因子，以刺激中枢神经系统细胞的LTR。所有这些观察结果为我们假设HIV-1通过其反激活子Tat与宿主重组修复调节因子Rad51的相互作用提供了理论基础，该相互作用创造了一个条件，导致小胶质细胞、星形胶质细胞和可能的巨噬细胞中HIV-1启动子的激活，并改变宿主重组修复途径，有利于HIV-1。在此申请中，我们寻求支持，以启动一系列良好整合的分子，病毒学和细胞研究，以破译与HIV-1和宿主DNA修复机制交叉通信相关的分子事件，并根据我们的观察制定策略，抑制支持病毒感染的细胞中HIV-1基因的表达和激活。在整个研究过程中，我们的分子发现与HIV-1神经发病机制的相关性将在每个阶段通过使用来自HIVE患者的独特脑标本收集（由曼哈顿脑库提供）进行验证。因此，通过这种新颖的综合方法，我们的研究将提供与HIV-1/CNS疾病相关的重要信息，可用于改进目前治疗艾滋病患者神经系统疾病的方法。

DESCRIPTION (provided by applicant): Infection of the central nervous system with HIV-1 can trigger a cascade of defense mechanisms that are aimed at blocking expression of the viral genome at various stages of its life cycle. In turn, HIV-1 has evolved several regulatory events via its accessory proteins, more notably Tat, to overcome the cellular defense pathways and through a series of diverse modulatory event induces maximum damage to the cells while ensuring a productive viral life cycle in the infected cells. Recently, much attention has been focused on the impact of HIV-1 infection on host cell homeostasis, more specifically the interaction of HIV-1 with cellular pathways that control chromosomal integrity via homologous and non-homologous DNA repair. While the role of HIV-1 Vpr in affecting DNA damage is well documented, recent observations (shown here) point to the ability of Tat in the induction of Rad51 expression in primary microglia and astrocytes, the two cell types that play an important role in neuropathogenesis of AIDS. This observation corroborates the results from infection studies showing increased levels of Rad51 in HIV-1 infected microglia and astrocytes in culture and in AIDS brain with HIV encephalitis. Rad51 is the major regulator of the homologous recombination repair pathway that in coordination with other cellular proteins ensures chromosomal integrity. Evidently, unscheduled activation of Rad51 may have an adverse impact on several cellular pathways and in some instances even compromise chromosomal integrity. Interestingly, induction of Rad51 by Tat protein may have a positive feedback effect on HIV-1 promoter activity in microglia and astrocytes. In this respect, our preliminary data point to the possible recruitment of NF-B and cyclin T1, the two regulators of HIV-1, by Rad51 for stimulation of the LTR in CNS cells. All these observations provide a rationale for us to hypothesize that the reciprocal interaction of HIV-1 through its transactivator, Tat, with the host recombination repair regulator, Rad51 creates a condition that leads to activation of the HIV-1 promoter in microglia, astrocytes and possibly macrophages, and alters host recombination repair pathways in favor of HIV-1. In this application, we seek support to launch a series of well-integrated molecular, virological, and cellular studies to decipher the molecular events associated with cross-communication of HIV-1 and host DNA repair machinery and develop a strategy, based on our observations, to inhibit HIV-1 gene expression and activation in cells that support viral infection. Throughout our studies the relevance of our molecular discoveries to the neuropathogenesis of HIV-1 will be verified at every stage through the use of a unique collection of brain specimens from HIVE patients (provided by the Manhattan Brain Bank). Thus, through this novel integrated approach, our studies will provide important information relevant to HIV-1/CNS diseases that can be used to improve the current method for treatment of AIDS patients with neurological disorders.