Bromodomain-containing protein 4 plays a central role in coordinating the complex epigenetic component of the innate immune response. Previous studies implicated BRD4 as a component of a chromatin-modifying complex that is dynamically recruited to a network of protective cytokines by binding activated transcription factors, polymerases, and histones to trigger their rapid expression via transcriptional elongation. Our previous study extended our understanding of the airway epithelial BRD4 interactome by identifying over 100 functionally important coactivators and transcription factors, whose association is induced by respiratory syncytial virus (RSV) infection. RSV is an etiological agent of recurrent respiratory tract infections associated with exacerbations of chronic obstructive pulmonary disease. Using a highly selective small-molecule BRD4 inhibitor (ZL0454) developed by us, we extend these findings to identify the gene regulatory network dependent on BRD4 bromodomain (BD) interactions. Human small airway epithelial cells were infected in the absence or presence of ZL0454, and gene expression profiling was performed. A highly reproducible dataset was obtained which indicated that BRD4 mediates both activation and repression of RSV-inducible gene regulatory networks controlling cytokine expression, interferon (IFN) production, and extracellular matrix remodeling. Index genes of functionally significant clusters were validated independently. We discover that BRD4 regulates the expression of its own gene during the innate immune response. Interestingly, BRD4 activates the expression of NFκB/RelA, a coactivator that binds to BRD4 in a BD-dependent manner. We extend this finding to show that BRD4 also regulates other components of its functional interactome, including the Mediator (Med) coactivator complex and the SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin (SMARC) subunits. To provide further insight into mechanisms for BRD4 in RSV expression, we mapped 7,845 RSV-inducible Tn5 transposase peaks onto the BRD4-dependent gene bodies. These were located in promoters and introns of cytostructural and extracellular matrix (ECM) formation genes. These data indicate that BRD4 mediates the dynamic response of airway epithelial cells to RNA infection by modulating the expression of its coactivators, controlling the expression of host defense mechanisms and remodeling genes through changes in promoter accessibility.

含溴结构域的蛋白质 4 在协调先天免疫反应的复杂表观遗传成分方面起着核心作用。先前的研究表明，BRD4 作为染色质修饰复合物的一个组成部分，通过结合激活的转录因子、聚合酶和组蛋白，通过转录延长触发它们的快速表达，从而动态地招募到保护性细胞因子网络中。我们之前的研究通过鉴定超过 100 种功能重要的共激活因子和转录因子，扩展了我们对气道上皮 BRD4 相互作用组的理解，它们的关联是由呼吸道合胞病毒 (RSV) 感染诱导的。RSV 是与慢性阻塞性肺疾病恶化相关的复发性呼吸道感染的病原体。使用我们开发的高选择性小分子 BRD4 抑制剂 (ZL0454)，我们扩展了这些发现以鉴定依赖于 BRD4 溴结构域 (BD) 相互作用的基因调控网络。在不存在或存在 ZL0454 的情况下感染人类小气道上皮细胞，并进行基因表达谱分析。获得了高度可重复的数据集，表明 BRD4 介导控制细胞因子表达、干扰素 (IFN) 产生和细胞外基质重塑的 RSV 诱导基因调控网络的激活和抑制。独立验证功能显着簇的索引基因。我们发现 BRD4 在先天免疫反应期间调节其自身基因的表达。有趣的是，BRD4 激活了 NFκB/RelA 的表达，一种以 BD 依赖性方式与 BRD4 结合的共激活剂。我们扩展了这一发现以表明 BRD4 还调节其功能性相互作用组的其他成分，包括介质 (Med) 共激活剂复合物和 SWI/SNF 相关、基质相关、肌动蛋白依赖性染色质 (SMARC) 亚基调节剂。为了进一步了解 BRD4 在 RSV 表达中的机制，我们将 7,845 个 RSV 诱导型 Tn5 转座酶峰映射到 BRD4 依赖性基因体上。这些位于细胞结构和细胞外基质 (ECM) 形成基因的启动子和内含子中。这些数据表明，BRD4 通过调节其共激活因子的表达、控制宿主防御机制的表达和通过启动子可接近性的变化来重塑基因来介导气道上皮细胞对 RNA 感染的动态反应。