TRANSCRIPTIONAL REGULATION BY EPIGENETIC FACTORS

表观遗传因素的转录调控

• 批准号: 7092638
• 负责人: ALEXANDER M MAZO
• 金额: $ 27.47万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7092638
• 关键词: DNA directed RNA polymerase; Drosophilidae; RNA interference; arthropod genetics; chromatin immunoprecipitation; developmental genetics; gene expression; gene induction /repression; genetic regulation; histones; homeobox genes; invertebrate embryology; microarray technology; molecular genetics; protein protein interaction; protooncogene; transcription factor

DESCRIPTION (provided by applicant): The mechanisms of gene regulation by the trithorax-group (trxG) and Polycomb-group (PcG) of proteins remain 1 of the most actively pursued issues in the current developmental and molecular biology. This continuous interest is based on the realization that these protein families are employed in regulation of a large number of important genes during development of the multicellular organisms, including the key regulators of early development, the homeotic (HOX) genes. TrxG and PcG proteins exert their activities by altering the chromatin structure of their target genes. This is achieved in a variety of ways, by either changing the packaging of nucleosomes by the ATP-dependent nucleosome remodeling complexes, or by the enzymatic modifications of a number of residues in histone tails. Importantly, irrespective of the specific ways in which TrxG and PcG proteins exert their activities, they are capable of locking in a specific status of gene expression, which is then inherited in an epigenetic fashion in daughter cells. The studies of these 2 groups of proteins have an important health-related applications since some of these proteins, as for example ALL1/HRX/MLL, are believed to be involved in a number of cancers. Our recent data suggest that the TrxG protein complex TAC1 is recruited to the region downstream of the start site of the actively transcribed heat shock genes. This recruitment is accompanied by the specific TAG 1-dependent methylation and acetylation of histone residues and ultimately leads to an increase in heat shock gene transcription. The goal of this proposal is to test the hypothesis that this mode of functioning of TAG 1 is also true for the developmentally regulated genes, by using a target HOX gene Ultrabithorax (Ubx) as a model. Our preliminary results indicate that a key component of this complex, Trithorax (TRX), is found downstream of the start site of Ubx and at its promoter, suggesting that TRX is involved in 2 different steps of transcription, initiation and elongation of transcription by Poll. Based on these and previous studies, and on the functional similarities with the homologous proto-oncogene MLL, we propose the existence of 2 TRX complexes that may be involved in these different aspects of transcription. Two (2) TRX complexes may interact with other factors that are required for initiation and/or elongation of transcription. To test this hypothesis and to uncover the role of TRX complexes in the network of other transcription factors, we developed a sorting technique that allows to obtain nuclei in which Ubx is activated and silenced. Using this technique, we propose to address the following questions: (i) What is the difference in association of the TrxG and PcG proteins with the regulatory regions of the transcriptionally active and silenced Ubx gene? (ii) What are the features of the new MLL-like TRX complex? (iii) Which steps of Ubx transcription require different TRX protein complexes? (iv) What are the roles of TRX complexes in the network of other transcription factors? Answers to these questions will shed new light not only on the way TAC1 exerts its effects during transcriptional regulation, but will also reveal the roles of other TrxG and PcG proteins in epigenetic maintenance, as well as the relationship of these epigenetic regulators with factors that are involved in initiation and elongation of RNA polymerase. Given structural and functional similarities between TRX and MLL, these studies will also advance our knowledge of the basic mechanisms of transcriptional regulation in eukaryotes and their relevance to diseases like cancer.

描述（由申请人提供）：蛋白质的三胸组（trxG）和多梳组（PcG）的基因调控机制仍然是当前发育和分子生物学中最积极研究的问题之一。这种持续的兴趣是基于这样的认识：这些蛋白质家族在多细胞生物发育过程中用于调节大量重要基因，包括早期发育的关键调节因子，即同源异型（HOX）基因。 TrxG 和 PcG 蛋白通过改变其靶基因的染色质结构来发挥其活性。这可以通过多种方式实现，通过 ATP 依赖性核小体重塑复合物改变核小体的包装，或通过组蛋白尾部的许多残基进行酶促修饰。重要的是，无论 TrxG 和 PcG 蛋白发挥其活性的具体方式如何，它们都能够锁定基因表达的特定状态，然后在子细胞中以表观遗传方式遗传。对这两类蛋白质的研究具有重要的健康相关应用，因为其中一些蛋白质，例如 ALL1/HRX/MLL，被认为与多种癌症有关。我们最近的数据表明，TrxG 蛋白复合物 TAC1 被招募到活跃转录的热休克基因起始位点的下游区域。这种募集伴随着组蛋白残基的特异性 TAG 1 依赖性甲基化和乙酰化，最终导致热休克基因转录增加。该提案的目的是通过使用目标 HOX 基因 Ultrabithorax (Ubx) 作为模型，检验 TAG 1 的这种功能模式对于发育调控基因也适用的假设。我们的初步结果表明，该复合物的关键成分 Trithorax (TRX) 存在于 Ubx 起始位点的下游及其启动子处，表明 TRX 参与 Poll 转录的 2 个不同步骤：转录起始和延伸。基于这些和之前的研究，以及与同源原癌基因 MLL 的功能相似性，我们提出可能涉及转录的这些不同方面的 2 个 TRX 复合物的存在。两 (2) 个 TRX 复合物可能与转录起始和/或延伸所需的其他因子相互作用。为了检验这一假设并揭示 TRX 复合物在其他转录因子网络中的作用，我们开发了一种分选技术，可以获取 Ubx 被激活和沉默的细胞核。使用这种技术，我们建议解决以下问题：（i）TrxG 和 PcG 蛋白与转录活性和沉默的 Ubx 基因的调控区域的关联有什么区别？ (ii) 新的类似 MLL 的 TRX 复合体有哪些特点？ (iii) Ubx 转录的哪些步骤需要不同的 TRX 蛋白复合物？ (iv) TRX 复合物在其他转录因子网络中的作用是什么？这些问题的答案不仅将为TAC1在转录调控过程中发挥其作用的方式提供新的线索，还将揭示其他TrxG和PcG蛋白在表观遗传维持中的作用，以及这些表观遗传调节因子与以下因子的关系：参与RNA聚合酶的起始和延伸。鉴于 TRX 和 MLL 之间的结构和功能相似性，这些研究还将增进我们对真核生物转录调控基本机制及其与癌症等疾病的相关性的了解。