SMC1A/3 cohesin complex-mediated silencing of unintegrated HIV-1 DNA and the antagonism by Vpr

摘要 人类免疫缺陷病毒(HIV-1)感染可导致致命的获得性免疫缺陷 综合症(艾滋病)。在HIV-1自然感染过程中，一些病毒DNA整合到宿主基因组中，但 绝大多数病毒DNA以一种未整合的状态存在。整合型HIV-1的转录调控 DNA在HIV-1感染和致病机制中起着重要作用。与强劲的病毒基因表达相反 在整合的病毒DNA中，染色体外的、未整合的病毒DNA转录很差。完全相同的 未整合的HIV-1DNA沉默的机制还不清楚，这构成了一个主要的 HIV-1研究中的知识差距。HIV-1辅助蛋白VPR增强鸡传染性支气管炎病毒基因表达 未整合的HIV-1DNA通过靶向宿主蛋白进行降解。在寻找vpr目标主持人因素(S) 可以沉默未整合的HIV-1DNA，我们已经进行了VPR靶标的CRISPR-Cas9基因敲除筛选 基因，并鉴定了NS1BP。我们还发现，NS1BP相互作用的伙伴SMC1A/3粘附素复合体是 沉默未整合的HIV-1DNA所需的。我们假设NS1BP作为辅助因子促进 SMC1A/3粘附素复合体在病毒DNA上的负载，导致病毒染色质紧凑和基因 抑制和VPR介导的NS1BP降解导致粘连蛋白复合体从 病毒DNA，从而抑制未整合的HIV-1 DNA的沉默。在这个项目中，我们将 确定NS1BP和SMC1A/3粘附素复合体介导沉默的机制 未整合的HIV-1DNA(AIM 1)，并阐明VPR拮抗沉默的机制 NS1BP和粘附素复合体(目标2)。我们建议的研究将极大地扩展我们对 整合型HIV-1 DNA转录调控的分子机制及提供新的研究方向 关于HIV-1DNA表观遗传沉默的信息。从长远来看，这些研究将提供新的 治疗HIV-1感染的目标和策略。

ABSTRACT Human immunodeficiency virus (HIV-1) infection can lead to the deadly disease acquired immunodeficiency syndrome (AIDS). During the natural infection of HIV-1, some viral DNAs are integrated into host genome, but the vast majority of viral DNAs exist in an unintegrated state. Transcriptional regulation of unintegrated HIV-1 DNA plays important roles in HIV-1 infection and pathogenesis. In contrast to the robust viral gene expression from integrated viral DNA, the extrachromosomal, unintegrated viral DNAs are very poorly transcribed. The exact mechanisms for the silencing of unintegrated HIV-1 DNA are not well understood, which constitutes a major knowledge gap in HIV-1 research. HIV-1 accessory protein Vpr enhances viral gene expression from unintegrated HIV-1 DNA by targeting host proteins for degradation. In search for Vpr target host factor(s) that can silence unintegrated HIV-1 DNA, we have performed a CRISPR-Cas9 knockout screening of Vpr target genes and identified NS1BP. We also found that NS1BP-interacting partner, the SMC1A/3 cohesin complex, is required for the silencing of unintegrated HIV-1 DNA. We hypothesize that NS1BP acts as a cofactor to facilitate the loading of the SMC1A/3 cohesin complex on viral DNA, which results in viral chromatin compaction and gene suppression, and Vpr-mediated degradation of NS1BP results in the dissociation of the cohesin complex from viral DNA, which consequently depresses the silencing of unintegrated HIV-1 DNA. In this project, we will determine the mechanism by which NS1BP and the SMC1A/3 cohesin complex mediate the silencing of unintegrated HIV-1 DNA (Aim 1), and elucidate the mechanism by which Vpr antagonizes the silencing mediated by NS1BP and the cohesin complex (Aim 2). Our proposed studies will significantly extend our understanding of the molecular mechanism for the transcriptional regulation of unintegrated HIV-1 DNA and provide new information regarding the epigenetic silencing of HIV-1 DNA. In the long term, these studies will provide new targets and strategies for the cure of HIV-1 infection.