Modulation of BRD4 to epigenetically suppress HIV

摘要 HIV病毒DNA整合到宿主细胞基因组中和建立稳定的潜伏感染提出了一种 找到艾滋病毒治疗方法的主要障碍。HIV在细胞库中的前病毒表达受宿主表观遗传调控 和转录机制。确定以主机为目标的有效方法，以破坏或 强制执行艾滋病毒潜伏期是一个重要目标。BRD4是一种表观遗传阅读器，属于溴域(BD) 和端外结构域(ET)蛋白家族(BET)。BRD4通过BDS与乙酰赖氨酸(KAc)残基结合 在染色质中组蛋白中，作为通过蛋白质-蛋白质招募伙伴蛋白质的支架平台 相互作用(PPI)调节基因转录，包括艾滋病毒。PAN-BET抑制剂对BET/BRD4的调制作用 (JQ1)以BDS中经典的Kac结合位点为靶点，已被证明能激活HIV转录。近期 我的团队和其他人的研究表明，BRD4在功能上是多功能的，它对基因转录的活性 是由它参与的特定伙伴蛋白定制的。利用结构辅助设计，我们的研究(1，2)已经确定 一个铅小分子(ZL0580)和几个与JQ1不同但能诱导HIV转录的类似物 通过BRD4进行抑制。我们证明ZL0580诱导抑制转录活性 以及多种细胞模型中的潜伏HIV，包括J-Lat、CD4T细胞和髓系细胞/小胶质细胞。对接分析 结合模式和机理研究表明，ZL0580与JQ1不同，它针对一个明显的新区域 BRD4 BD1结合[非乙酰赖氨酸(KAc)位点]并通过抑制诱导HIV转录抑制 TAT反式激活和诱导HIV LTR的抑制性染色质结构。基于这些小说 发现，我们的中心假设是宿主BRD4及其相关的表观遗传机制可以被调节 以抑制艾滋病毒，导致强制艾滋病毒潜伏期。除了ZL0580，我们正在进行的研究发现了另一个 类似物(YL0255)，在结构上接近ZL0580，并诱导更强的HIV抑制。在此应用程序中， 我们将使用ZL0580和YL0255作为两个新的分子探针来系统地研究BRD4的调控 在艾滋病毒表观遗传抑制方面。在目标1中，我们将确定BRD4是否是选择性的蛋白质靶标 ZL0580/YL0255和基础结构基础。在目标2中，我们将通过以下方式阐明分子机制 ZL0580/YL0255对BRD4的调控可诱导HIV表观遗传抑制。在《目标3》中，作为 在这个概念中，我们将检查ZL0580/YL0255对BRD4的调制是否诱导体内潜伏的HIV抑制。 总的来说，这些研究对于更好地理解艾滋病毒表观遗传调控和潜伏期至关重要，并将为 为未来制定新的策略以诱导抑制和/或沉默艾滋病毒奠定了关键基础。

ABSTRACT Integration of HIV viral DNA into host cell genomes and establishment of stable latent infection have posed a major obstacle for finding an HIV cure. HIV proviral expression in cell reservoirs is regulated by host epigenetic and transcriptional mechanisms. Identification of effective approaches targeting host machineries to disrupt or enforce HIV latency is a significant goal. BRD4 is an epigenetic reader that belongs to the bromodomain (BD) and extra-terminal domain (ET) protein family (BET). Via the BDs, BRD4 binds to acetyl-lysine (KAc) residues in chromatin histones and serves as a scaffolding platform for recruiting partner proteins through protein-protein interactions (PPI) to regulate gene transcription, including HIV. Modulation of BET/BRD4 by a pan-BET inhibitor (JQ1), which targets the classic KAc binding site in BDs, has been shown to activate HIV transcription. Recent studies by my group and others indicate that BRD4 is functionally versatile, and its activity on gene transcription is tailored by specific partner proteins it engages. Using structure-aided design, our studies (1, 2) have identified a lead small molecule (ZL0580) and several analogs that are distinct from JQ1 but induce HIV transcriptional suppression through BRD4. We demonstrate that ZL0580 induces suppression of both transcriptionally active and latent HIV in multiple cell models, including J-Lat, CD4 T cells and myeloid cells/microglia. Docking analyses of binding modes and mechanistic investigations indicate that unlike JQ1, ZL0580 targets a distinct new region of BRD4 BD1 for binding [non-acetyl-lysine (KAc) site] and induces HIV transcriptional suppression by inhibiting Tat transactivation and by inducing a repressive chromatin structure at the HIV LTR. Based on these novel findings, our central hypothesis is that host BRD4 and its associated epigenetic machinery can be modulated to repress HIV, leading to enforced HIV latency. Other than ZL0580, our ongoing research has identified another analog (YL0255) that is structurally close to ZL0580 and induces stronger HIV suppression. In this application, we will use ZL0580 and YL0255 as two novel molecular probes to systemically investigate modulation of BRD4 in HIV epigenetic suppression. In Aim 1, we will determine if BRD4 is a selective protein target for ZL0580/YL0255 and the underlying structural basis. In Aim 2, we will elucidate the molecular mechanisms by which modulation of BRD4 by ZL0580/YL0255 induces HIV epigenetic suppression. In Aim 3, as a proof of concept, we will examine if modulation of BRD4 by ZL0580/YL0255 induces repression of latent HIV in vivo. Collectively, these studies are critical for better understanding HIV epigenetic regulation and latency and will lay critical groundwork for developing novel strategies for inducing HIV suppression and/or silencing in future.