Cardiomyocyte bromodomain protein 4 (BRD4) in physiology and disease

心肌细胞溴结构域蛋白 4 (BRD4) 在生理学和疾病中的作用

• 批准号: 10241315
• 负责人: JOSEPH A HILL
• 金额: $ 61.98万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10241315
• 关键词: Acetylation; Biology; Bromodomain; C-terminal; Cardiac; Cardiac Myocytes; Cardiac development; Cardiovascular system; Cells; ChIP-seq; Chromatin; Chromatin Structure; Clinical; Coupled; Cues; Data; Dilated Cardiomyopathy; Disease; Endogenous Factors; Engineering; Enhancers; Epigenetic Process; Event; Exons; Family; Family member; Fostering; Gene Expression; Gene Expression Profile; Genes; Genetic Transcription; Growth; HDAC1 gene; Heart; Heart Hypertrophy; Heart failure; Homeostasis; In Vitro; Knockout Mice; Literature; Mitochondria; Oncology; Outcome; Pathogenesis; Pathologic; Pathology; Pathway interactions; Phase; Phenotype; Physiology; Play; Positive Transcriptional Elongation Factor B; Post-Translational Protein Processing; Process; Protein Family; Protein Isoforms; Proteins; RNA Interference; Reader; Reperfusion Injury; Role; Small Interfering RNA; Stress; Structure; Therapeutic; Transcription Alteration; Transcriptional Regulation; Transgenic Mice; Variant; Ventricular; Work; base; cardioprotection; epigenetic therapy; heart function; histone modification; in vitro Model; in vivo; interest; knock-down; knockout animal; mouse model; pressure; response; small molecule; small molecule inhibitor; tool; transcriptome sequencing

Project Summary Together with the effects of modifier genes, sequence variants, endogenous factors, and environmental cues, strong evidence points to epigenetic events contributing to heart failure pathogenesis. Furthermore, epigenetic therapies have emerged already in oncology. Work from our lab and others has demonstrated robust cardioprotective effects of small molecule inhibitors of class 1 histone deacetylases (acetyl “erasers”) in both pressure-overload stress and ischemia/reperfusion injury. In this proposal, we will turn our focus to the so-called “readers“ of acetylation, the BRD proteins, specifically BRD4. Prior work in the literature has demonstrated that a small molecule inhibitor of BRD proteins blunts pathological cardiac remodeling, raising the tantalizing prospect of targeting this biology for therapeutic gain. Depletion of specific BRD isoforms in those studies implicated BRD4. Importantly, BRD4 encodes at least two isoforms in the heart (BRD-L and BRD-S) via alternative exon usage. The long isoform BRD4-L is unique in the BET family in that it contains an extended C terminus that includes a P-TEFb-interacting domain. BRD4 is known to regulate superenhancers, large clusters of transcriptional enhancers that drive expression of genes that define cell identity. Indeed, BRD4-L is required for super-enhancer function, with the C-terminal domain necessary for the phase-shift occurring with formation of super-enhancer clusters. The short isoform BRD4-S lacks this C terminus. Beyond these structural differences, it is clear in the context of oncology and other domains that these BRD4 isoforms have distinct – indeed antagonistic – functions, a fact which complicates the interpretation of existing data in the cardiovascular space. Presently, nothing is known about the role of these BRD4 isoforms in the heart. Our preliminary data, using a cardiomyocyte-specific BRD4 knockout mouse, show that loss of BRD4 results in a rapid decline in ventricular contractile function and dilated cardiomyopathy. Our preliminary in vitro studies and in vivo studies targeting specific BRD4 isoforms suggests that BRD4-L is not required for cardiac hypertrophy, but rather, the hypertrophic response is dependent on BRD4-S. Here, we propose work based on the over-riding hypothesis that specific isoforms of BRD4 play distinct roles in cardiomyocyte physiology and pathology. Work to unveil isoform-specific functions will be a major step toward precision targeting of this biology in disease therapy. Already, we have developed unique tools to directly assess the roles of these isoforms both in vitro and in vivo.

项目概要 连同修饰基因、序列变异、内源因素和 环境线索，强有力的证据表明表观遗传事件导致心力衰竭 发病。此外，表观遗传疗法已经在肿瘤学中出现。工作自 我们的实验室和其他实验室已经证明小分子抑制剂具有强大的心脏保护作用 1 类组蛋白脱乙酰酶（乙酰“擦除器”）在压力过载应激和 缺血/再灌注损伤。在这个提案中，我们将把重点转向所谓的“读者” 乙酰化，BRD 蛋白，特别是 BRD4。 先前的文献工作已经证明 BRD 蛋白的小分子抑制剂 削弱病理性心脏重塑，提高了针对这种生物学的诱人前景 以获得治疗收益。这些研究中特定 BRD 同工型的耗尽与 BRD4 有关。 重要的是，BRD4 在心脏中至少编码两种亚型（BRD-L 和 BRD-S） 替代外显子的使用。长亚型 BRD4-L 在 BET 家族中是独一无二的，因为它包含 包含 P-TEFb 相互作用结构域的扩展 C 末端。 BRD4 已知可调节 超级增强子，驱动基因表达的大簇转录增强子 定义细胞身份。事实上，BRD4-L 是超级增强子功能所必需的，其 C 端 形成超级增强器簇时发生相移所必需的域。这 短异构体 BRD4-S 缺少该 C 末端。 除了这些结构差异之外，在肿瘤学和其他领域的背景下这一点也很明显 这些 BRD4 异构体具有独特的——实际上是拮抗的——功能，这一事实 使心血管领域现有数据的解释变得复杂。目前，没有什么是 了解这些 BRD4 同工型在心脏中的作用。 我们使用心肌细胞特异性 BRD4 敲除小鼠的初步数据表明，损失 BRD4 的减少会导致心室收缩功能迅速下降和扩张型心肌病。 我们针对特定 BRD4 亚型的初步体外研究和体内研究表明 BRD4-L 不是心脏肥大所必需的，而是肥厚反应是 依赖于 BRD4-S。在这里，我们提出基于最重要的假设的工作： BRD4 的特定亚型在心肌细胞生理学和 病理。揭示异构体特异性功能的工作将是迈向精确性的重要一步 在疾病治疗中以这种生物学为目标。我们已经开发了独特的工具来直接 评估这些亚型在体外和体内的作用。