Transcriptional repression by Polycomb Repressive Complex 2

项目摘要 这个项目的长期目标是了解被抑制的染色质状态的组装，并 阐明在这些特殊的染色质环境中基因抑制的机制。复梳群 (PCG)蛋白相互作用形成酶复合体，从而修饰染色质并组装抑制的染色质 在动物、植物和大多数真菌中的状态。多梳抑制复合体2(PRC2)是一种高度保守的 组蛋白赖氨酸-27甲基转移酶复合体，对多细胞发育至关重要，并发挥关键作用 在维持干细胞鉴定、X染色体失活和基因调控中的作用。突变 PRC2功能改变与人类Weaver综合征和多种癌症有关。尽管它的 重要的是，我们缺乏对控制PRC2和抑制转录的机制的清楚了解 PRC2靶基因。对模式真菌粗枝脉孢菌的初步研究已经开始解决 这些关键的知识差距。脉孢子虫是一种功能强大的实验系统，具有共同的关键特征 更高级的真核生物。也就是说，PRC2的组件在结构和功能上是保守的，而 它们在两种主要酵母--酿酒酵母和裂殖酵母中都缺乏。一个 400多株缺乏已知或预测的粗链球菌基因缺失的靶向RNA测序筛选 染色质相关蛋白或染色质调节蛋白发现PcG抑制所需的新基因 并开始对它们的功能产生机械性的见解。遗传、分子、 蛋白质组学和基因组学方法将利用这些新发现，生物信息学分析将 询问这个独特的RNA-seq数据集以：1)确定一个保守的依赖于ATP的染色质 重塑酶控制PrC2和PcG抑制结构域的基因抑制，2)确定机制 其中构成异染色质成分调节PrC2，以及3)定义一个全面的PcG 染色质网络在一个简单的模型系统中。成功完成拟议的目标将揭开 控制PcG抑制的染色质结构域组装和功能的一般原理和机制。 由于PcG介导的沉默的前两个新发现的成分是保守的，来自 拟议的研究将为未来对包括人类在内的高等真核生物的研究提供一个框架。 此外，由于PcG蛋白与癌症和其他遗传性疾病有关，因此了解 这些关键的染色质调节因子的调节和功能最终将改善急性淋巴细胞白血病的诊断和治疗 人类疾病。

Project Summary The long-term goals of this project are to understand assembly of repressed chromatin states and to elucidate mechanisms of gene repression in these specialized chromatin environments. Polycomb Group (PcG) proteins interact to form enzyme complexes that modify chromatin and assemble repressed chromatin states in animals, plants, and most fungi. Polycomb Repressive Complex 2 (PRC2) is a highly conserved histone lysine-27 methyltransferase complex that is essential for multicellular development and plays key roles in maintenance of stem cell identify, X-chromosome inactivation, and gene regulation. Mutations that alter PRC2 function are responsible for human Weaver syndrome and multiple cancers. Despite its importance, we lack a clear understanding of the mechanisms that control PRC2 and repress transcription of PRC2 target genes. Preliminary studies with the model fungus Neurospora crassa have begun to address these critical gaps in knowledge. Neurospora is a powerful experimental system that shares key features with higher eukaryotes. Namely, components of PRC2 are structurally and functionally conserved, while they are lacking in both major yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe. A targeted RNA-sequencing screen of over 400 N. crassa gene deletion strains that lack known or predicted chromatin-associated or chromatin regulatory proteins uncovered new genes required for PcG repression and are beginning to yield mechanistic insights into their functions. Application of genetic, molecular, proteomic, and genomic approaches will capitalize on these novel findings, and bioinformatic analyses will interrogate this unique RNA-seq data set to: 1) determine how a conserved ATP-dependent chromatin remodeling enzyme controls PRC2 and gene repression at PcG-repressed domains, 2) define mechanisms by which constitutive heterochromatin components regulate PRC2, and 3) define a comprehensive PcG chromatin network in a simple model system. Successful completion of the proposed aims will uncover general principles and mechanisms governing assembly and function of PcG-repressed chromatin domains. Because the first two newly identified components of PcG-mediated silencing are conserved, findings from the proposed studies will serve as a framework for future studies in higher eukaryotes, including humans. In addition, because PcG proteins are linked to cancer and other genetic diseases, understanding the regulation and function of these key chromatin regulators will ultimately improve diagnosis and treatment of human disease.