TRANSCRIPTIONAL REGULATION BY EPIGENETIC FACTORS

表观遗传因素的转录调控

• 批准号: 6961404
• 负责人: ALEXANDER M MAZO
• 金额: $ 31.47万
• 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/6961404
• 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Trithorax-group（TRXG）和Polycomb-group（PCG）的基因调节机制仍然是当前发育和分子生物学中最积极的问题之一。这种持续的兴趣是基于认识到这些蛋白质家族在多细胞生物的发育过程中使用大量重要基因的认识，包括早期发育的关键调节剂，同源（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。这是通过多种方式来实现的，要么通过通过ATP依赖性核小体重塑复合物或组蛋白尾部中许多残基的酶促修饰来改变核小体的包装。重要的是，无论TRXG和PCG蛋白发挥其活性的特定方式如何，它们都能锁定基因表达的特定状态，然后以子细胞的表观遗传方式遗传。这两组蛋白质的研究具有重要的健康相关应用，因为这些蛋白质中的某些（例如All1/HRX/MLL）据信与许多癌症有关。我们最近的数据表明，TRXG蛋白复合物TAC1被募集到主动转录热休克基因开始部位的下游区域。该募集伴随着特定的TAG 1依赖性甲基化和组蛋白残基的乙酰化，并最终导致热休克基因转录的增加。该提案的目的是检验以下假设：通过将目标HOX基因Ultrabithorax（UBX）作为模型，TAG 1的这种功能模式对于开发调节的基因也是如此。我们的初步结果表明，该复合物Trithorax（TRX）的关键组成部分是在UBX及其启动子开始的下游，这表明TRX参与了通过Poll通过Poll的2个不同的转录，开始和转录的延伸。基于这些和以前的研究，以及与同源原始癌基因MLL的功能相似性，我们提出了可能与转录的这些不同方面有关的2个TRX复合物的存在。两（2）个TRX复合物可能与转录启动和/或伸长所需的其他因素相互作用。为了检验这一假设并发现TRX复合物在其他转录因子网络中的作用，我们开发了一种分类技术，允许获得UBX激活和沉默的核。使用此技术，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基因的调节区域的关联差异是什么？ （ii）新型MLL样TRX复合物的功能是什么？ （iii）UBX转录的哪个步骤需要不同的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会在TAC1在转录调控过程中发挥其影响的方式，而且还将揭示其他TRXG和PCG蛋白在表观遗传学维持中的作用，以及这些表观遗传调节剂与涉及RNA聚合酶启动和促进的因素的关系。鉴于TRX和MLL之间的结构和功能相似性，这些研究还将提高我们对真核生物转录调控的基本机制及其与癌症等疾病的相关性的了解。