De novo establishment of Polycomb-group-mediated repression

从头开始建立多梳基团介导的抑制

• 批准号: 7981379
• 负责人: RICHARD S JONES
• 金额: $ 42.67万
• 依托单位: SOUTHERN METHODIST UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7981379
• 关键词: Binding; Biochemical; Blastoderm; Cell Culture Techniques; Cell Cycle; Cells; Complement; DNA Binding; Development; Drosophila genus; Ectopic Expression; Embryo; Embryonic Development; Enhancers; Epigenetic Process; Epithelial; Event; Female; Gene Expression; Gene Silencing; Gene Targeting; Generations; Genes; Genetic; Genetic Transcription; Goals; Histone H3; Human; Insecta; Lead; Learning; Location; Lysine; Maintenance; Malignant Neoplasms; Mammals; Maps; Mediating; Modeling; Molecular; Nucleic Acid Regulatory Sequences; Oncogenic; Organism; Orthologous Gene; PRC1 Protein; Pattern; Phase; Play; Polycomb; Population; Prostate; Proteins; Recruitment Activity; Regulator Genes; Reporter; Repression; Response Elements; Role; Staging; Stem cells; System; Testing; Time; Transgenic Organisms; chromatin immunoprecipitation; gene repression; genetic manipulation; genetic regulatory protein; imaginal disc; induced pluripotent stem cell; insight; malignant breast neoplasm; molecular dynamics; mutant; overexpression; protein complex; protein distribution; public health relevance; response; therapy development; tool; transcription factor; tumorigenesis

DESCRIPTION (provided by applicant): Polycomb-group (PcG) proteins comprise an epigenetic system that maintains the transcriptional repression of target genes. Originally identified as negative regulators of Drosophila Hox genes, their functions and molecular/biochemical activities have been highly conserved from insects to mammals. Mammalian PcG orthologs are required to maintain the pluripotent state of stem cells and their misexpression contributes to oncogenesis. PcG proteins do not initiate transcriptional repression, but rather take over repression from gene-specific transcription factors. Once PcG- mediated repression is established, it is then capable of stably and heritably maintaining gene silence through numerous cell cycles. During the maintenance phase of PcG-mediated repression, DNA binding PcG proteins (e.g., Pleiohomeotic) bind to sequences within Polycomb Response Elements (PREs) and recruit additional PcG protein complexes, such as PRC2, which in turn methylates histone H3 at lysine 27 (H3K27me3), facilitating recruitment of PRC1. Virtually nothing is known about the mechanisms by which PcG proteins initially recognize the repressed state of target genes and the molecular steps that lead to establishment of PcG-mediated repression. In large part, this is due to the heterogeneous expression of target genes within embryos during the developmental stages when PcG-mediated repression is established. In the proposed studies, genetic manipulation will be used to obtain syncytial and cellular blastoderm stage embryos in which a PcG target gene is ubiquitously repressed at the syncytial blastoderm stage by a maternally expressed transcription factor, and in which the PcG is required to maintain its ubiquitous repression by the cellular blastoderm stage. Two specific aims are proposed: (1) Map the locations of PREs within the regulatory region of the PcG target gene; (2) Define the physical and temporal distributions of regulatory proteins, including PcG proteins, at the PcG target gene during the developmental window when PcG-mediated repression is established. The goal of these studies is to provide insight into the molecular and biochemical steps involved in the transition from initial transcription factor-mediated repression to PcG-mediated maintenance of transcriptional silence. These results will be particularly relevant to the generation of iPS cells and oncogenesis, both of which involve de novo establishment of PcG-mediated repression. PUBLIC HEALTH RELEVANCE: Polycomb-group proteins are highly conserved negative regulators of gene expression, which maintain the silence of numerous developmentally important genes in organisms ranging from fruit flies to humans. Overexpression of Polycomb-group proteins contributes to a range of human cancers, including metastatic prostate and aggressive breast cancers as well as hematologic and epithelial cancers. The proposed studies will provide greater insight into the molecular mechanisms by which Polycomb-group- mediated repression is initially established, which may lead to the development of therapies that inhibit their activities, blocking their oncogenic effects.

描述（由申请人提供）：多梳组（PcG）蛋白包含维持靶基因转录抑制的表观遗传系统。Hox基因最初被鉴定为果蝇Hox基因的负调控因子，其功能和分子/生化活性从昆虫到哺乳动物都高度保守。哺乳动物PcG直系同源物是维持干细胞多能状态所必需的，并且它们的错误表达有助于肿瘤发生。PcG蛋白不启动转录抑制，而是从基因特异性转录因子接管抑制。一旦建立PcG介导的阻遏，它就能够在许多细胞周期中稳定地和遗传地维持基因沉默。在PcG介导的阻遏的维持阶段，DNA结合PcG蛋白（例如，PcG蛋白复合物（PcG蛋白复合物）与多梳应答元件（PRE）内的序列结合，并募集额外的PcG蛋白复合物，如PRC 2，PRC 2又使组蛋白H3在赖氨酸27处甲基化（H3 K27 me 3），促进PRC 1的募集。事实上，PcG蛋白最初识别靶基因的抑制状态的机制以及导致建立PcG介导的抑制的分子步骤一无所知。在很大程度上，这是由于在发育阶段，当建立PcG介导的阻遏时，胚胎内靶基因的异质表达。在所提出的研究中，将使用遗传操作来获得合胞体和细胞胚盘阶段胚胎，其中PcG靶基因在合胞体胚盘阶段被母体表达的转录因子普遍抑制，并且其中PcG需要维持其在细胞胚盘阶段的普遍抑制。提出了两个具体的目标：（1）映射的PcG靶基因的调控区域内的PRE的位置;（2）定义的物理和时间分布的调节蛋白，包括PcG蛋白，在发育窗口期间，当PcG介导的抑制建立在PcG靶基因。这些研究的目的是提供洞察的分子和生物化学的步骤参与从初始转录因子介导的抑制PcG介导的维持转录沉默的过渡。这些结果将是特别相关的iPS细胞的产生和肿瘤发生，这两个涉及从头建立PcG介导的抑制。 公共卫生相关性：多梳族蛋白是高度保守的基因表达负调控因子，在从果蝇到人类的生物体中维持许多发育重要基因的沉默。Polycomb组蛋白的过表达导致一系列人类癌症，包括转移性前列腺癌和侵袭性乳腺癌以及血液和上皮癌。拟议的研究将提供更深入的了解Polycomb组介导的抑制最初建立的分子机制，这可能导致抑制其活性的疗法的发展，阻断其致癌作用。