Mechanism of BET Proteins in Th17 Cell Differentiation

 描述（申请人提供）：由Brd 2、Brd 3、Brd 4和睾丸特异性Brdt组成的溴结构域和末端外结构域（BET）家族蛋白被广泛认为是生物学中的主要转录调节因子，这是由于它们的两个特征性串联溴结构域（BrD）结合活化的赖氨酸乙酰化组蛋白和转录因子以将转录因子/效应物募集到靶基因位点，并激活RNA聚合酶II机制以进行转录延伸。用泛BET BrD抑制剂如JQ 1对BET蛋白的药理学抑制已显示在生物学和人类癌症和炎症疾病模型中广泛阻断基因转录。然而，尽管它们具有突出的重要性，但我们目前对BET蛋白质的功能差异的了解仍然难以捉摸，从而严重阻碍了它们作为新疾病治疗的可行表观遗传药物靶标的潜力。因此，我们建议确定BET蛋白在T辅助细胞17（Th 17）细胞分化中的基因转录调控的功能机制，该细胞分化与炎症性疾病有关。我们的研究是建立在我们最近发现Brd 2和Brd 4在Th 17细胞中具有不同的基因组沉积，并且即使在它们共同调节转录的基因上也发挥不同的功能。重要的是，我们发现使用我们新开发的BrD抑制剂选择性抑制BET蛋白的第一布罗莫结构域主要阻碍Th 17细胞分化，对Th 1、Th 2和Treg细胞的影响最小，并且还预防小鼠中的适应性T细胞转移诱导的结肠炎。这些有利的发现促使我们确定Brd 2和Brd 4在Th 17细胞发育中功能的详细分子机制，并建立新的炎症性疾病治疗策略。具体而言，我们旨在实现三个具体目标：（1）确定BET蛋白在Thl 7细胞的基因转录中的不同机制作用;（2）开发BET BrD的新型化学调节剂;以及（3）表征BET蛋白在Thl 7细胞分化中的基因组功能。我们设想我们的研究不仅产生新的机制的见解Brd 2和Brd 4功能的转录调控Th 17细胞发育的适应性免疫，但也提供了一个更明确的方向，为开发更有效的治疗炎症性疾病的治疗。

 DESCRIPTION (provided by applicant): The bromodomain and extra-terminal domain (BET) family proteins, consisting of Brd2, Brd3, Brd4 and testis-specific Brdt, are widely recognized as major transcriptional regulators in biology, owing to their two characteristic tandem bromodomains (BrDs) binding to activated, lysine-acetylated histones and transcription factors to recruit transcription factors/effectors to target gene sites, and activate RNA polymerase II machinery for transcriptional elongation. Pharmacological inhibition of the BET proteins with pan-BET BrD inhibitors such as JQ1 has been shown to block broadly gene transcription in biology, and human cancer and inflammation disease models. Despite their prominent importance, however, our current knowledge of functional distinctions of the BET proteins has remained elusive, thus seriously hampering their potential as viable epigenetic drug targets for new disease treatment. As such, we propose to determine functional mechanisms of the BET proteins in gene transcriptional regulation in T-helper 17 (Th17) cell differentiation that has bee implicated in inflammatory disorders. Our study is built upon our recent discovery that Brd2 and Brd4 have distinct genomic deposition in Th17 cells, and exert different functions even at genes whose transcription they co-regulate. Importantly, we found that selective inhibition of the first bromodomain of BET proteins using our newly developed BrD inhibitor hinders primarily Th17 cell differentiation with beneficially minimal effects on Th1, Th2 and Treg cells, and also prevents adaptive T-cell transfer-induced colitis in mice. These favorable findings motivate us to determine the detailed molecular mechanisms of Brd2 and Brd4 functions in Th17 cell development, and establish a new therapeutic strategy for inflammatory disorders. Specifically, we aim to achieve three specific aims: (1) determine distinct mechanistic roles of the BET proteins in gene transcription of Th17 cells; (2) develop novel chemical modulators for BET BrDs; and (3) characterize genomic functions of BET proteins in Th17 cell differentiation. We envision our study not only to yield new mechanistic insights into Brd2 and Brd4 functions in transcriptional regulation of Th17 cell development in adaptive immunity, but also provide a clearer direction for developing more effective therapeutic treatment for inflammatory disorders.