TRANSCRIPTIONAL REGULATION BY EPIGENETIC FACTORS

表观遗传因素的转录调控

• 批准号: 7476459
• 负责人: ALEXANDER M MAZO
• 金额: $ 27.48万
• 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 2009-12-13
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7476459
• 关键词: Address; Animals; Cell Cycle; Cell Nucleus; Cell physiology; Chromatin; Chromatin Structure; Complex; DNA Polymerase II; DNA-Directed RNA Polymerase; Data; Development; Disease; Drosophila Proteins; Embryo; Epigenetic Process; Eukaryota; Eukaryotic Cell; Gene Expression; Gene Expression Regulation; Gene Targeting; Genes; Genetic Transcription; Goals; Heat-Shock Response; Histone Acetylation; Histones; Homeobox Genes; Inherited; Knowledge; Light; Maintenance; Malignant Neoplasms; Methylation; Modeling; Modification; Molecular Biology; Nucleic Acid Regulatory Sequences; Nucleosomes; Numbers; Organism; Polycomb; Process; Protein Family; Proteins; Proto-Oncogenes; Purpose; Recruitment Activity; Regulation; Regulatory Element; Repression; Role; Site; Sorting - Cell Movement; TAC1 gene; Tail; Techniques; Testing; Transcription Elongation; Transcription Initiation; Transcriptional Activation; Transcriptional Regulation; base; daughter cell; insight; interest; promoter; 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追求的问题之一。这种持续的兴趣是基于这样的认识，即这些蛋白质家族在多细胞生物体发育期间用于调节大量重要基因，包括早期发育的关键调节因子，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，或通过组蛋白尾部中许多残基的酶促修饰。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。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一些，例如ALL1/HRX/MLL，被认为与许多癌症有关。我们最近的数据表明，TrxG蛋白复合物TAC 1被募集到活跃转录的热休克基因的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，并最终导致热休克基因转录的增加。该提议的目的是通过使用靶HOX基因Ultrabithorax（Ubx）作为模型来检验TAG 1的这种功能模式对于发育调节基因也是真实的这一假设。我们的初步研究结果表明，该复合物的一个关键组成部分，Trithorax（TRX），被发现下游的起始位点的Ubx和其启动子，这表明TRX参与2个不同的转录步骤，启动和延长的Poll转录。基于这些和以前的研究，并与同源原癌基因MLL的功能相似性，我们提出了存在2 TRX复合物，可能参与这些不同方面的转录。两（2）种TRX复合物可与转录起始和/或延伸所需的其它因子相互作用。为了验证这一假设并揭示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，可以获得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：（一）什么是在协会的TrxG和PcG蛋白与转录活性和沉默的Ubx基因的调控区的差异？(ii)新的MLL-like TRX复合物有什么特点？(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揭示TAC1在转录调控过程中发挥作用的方式，而且还将揭示其他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RNA聚合酶启动和延伸相关因子的关系。鉴于TRX和MLL之间的结构和功能相似性，这些研究也将推进我们对真核生物转录调控基本机制及其与癌症等疾病相关性的认识。