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(申请人提供)：蛋白质的三胸基团(TrxG)和多梳基(PcG)的基因调控机制仍然是当前发育和分子生物学中最活跃的问题之一。这种持续的兴趣是基于这样的认识：在多细胞生物体的发育过程中，这些蛋白质家族被用来调节大量重要的基因，包括早期发育的关键调控基因，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。这是通过多种方式实现的，要么是通过依赖于ATP的核小体重塑复合体改变核小体的包装，要么是通过对组蛋白尾部的一些残基进行酶修饰。重要的是，无论TrxG和PcG蛋白发挥作用的具体方式如何，它们都能够锁定特定的基因表达状态，然后在子细胞中以表观遗传的方式遗传。对这两组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，如ALL1/HRX/MLL，被认为与许多癌症有关。我们最近的数据表明，TrxG蛋白复合体Tac1被招募到活跃转录的热休克基因起始点下游区域。这种招募伴随着组蛋白残基的特异性Tag1依赖的甲基化和乙酰化，最终导致热休克基因转录的增加。这项建议的目的是通过使用目标HOX基因Ultrabithorax(UBx)作为模型来检验TAG 1的这种功能模式对发育调节基因也适用的假设。我们的初步结果表明，该复合体的关键成分Trithorax(Trx)位于Ubx起始点下游及其启动子上，这表明Trx参与了Poll转录的启动和延伸两个不同的步骤。基于这些研究和前人的研究，以及与同源原癌基因MLL在功能上的相似性，我们提出了可能参与这些不同转录过程的两个Trx复合体的存在。两(2)个TrX复合体可能与启动和/或延长转录所需的其他因子相互作用。为了验证这一假设并揭示Trx复合体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被激活和沉默的核。利用这一技术，我们建议解决以下问题：(1)TrxG和PcG蛋白与转录活跃和沉默的Ubx基因的调控区有什么不同？(Ii)新的类似MLL的TRX综合体有哪些特点？(Iii)Ubx转录的哪些步骤需要不同的Trx蛋白复合体？(Iv)Trx复合体在其他转录因子网络中的作用是什么？对这些问题的回答不仅将揭示Tac1在转录调控过程中发挥作用的方式，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控因子与参与RNA聚合酶起始和延伸的因素的关系。鉴于Trx和MLL在结构和功能上的相似性，这些研究也将促进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。