Determination of a Novel Epigenetic Silencing Mechanism

 描述（由申请人提供）：表观基因组调节生物体何时、何地以及如何使用其基因组中存储的遗传信息。它对许多细胞过程至关重要，例如基因表达的调节，基因组组织和细胞命运决定。它还控制着生长、发育，最终控制着人类的健康。异染色质代表沉默的染色质结构域，其通过表观遗传机制组装和维持。大量的研究集中在由RNA干扰（RNAi）途径介导的异染色质在着丝粒的组装上。最近的研究，包括我们的研究，表明外泌体，RNA质量控制和监视复合物，在一个平行的途径与RNAi介导表观遗传沉默。虽然RNAi和外泌体途径都是RNA介导的，并参与将长非编码RNA（ncRNA）加工成小RNA，但外泌体途径如何参与异染色质组装尚未得到证实。其他RNAi非依赖性RNA加工途径是否参与表观遗传沉默也是未知的。 我们最近发现了表观遗传沉默中的RNA加工机制，其工作独立于RNA干扰和外泌体。所提出的研究目的旨在检验以下假设：Dhp 1是一种保守的5'至3'核糖核酸外切酶，是芽殖酵母Rat 1和后生动物Xrn 2的直系同源物，在表观遗传沉默中起着迄今为止未知的作用，超出了其在转录终止中的既定作用。将采用遗传学、细胞生物学和基因组学方法研究：1）Dhp 1在异染色质区域的定位; 2）Dhp 1结合蛋白; 3）Dhp 1的酶活性和表观遗传沉默中的潜在共激活剂。结果将阐明各种RNA加工途径，共同或独立地发挥作用，有助于真核基因组的表观遗传调控，基因表达的基本机制。本研究将在裂殖酵母，裂殖酵母粟酒裂殖酵母（S。pombe），由于其保守的表观遗传组分和适用于强大的组合实验方法以及本科研究，是研究表观遗传沉默的首要模型。 该项目具有重大意义和创新性。它将在表观遗传沉默中定义一种新的RNA加工机制，该机制独立于RNAi和外泌体。此外，这将是第一次探索Dhp 1/Rat 1/Xrn 2如何在基于染色质的沉默中发挥作用。

 DESCRIPTION (provided by applicant): The Epigenome regulates when, where and how an organism uses the genetic information stored in its genome. It is essential to many cellular processes, such as the regulation of gene expression, genome organization and cell-fate determination. It also governs growth, development, and ultimately human health. Heterochromatin represents silenced chromatic domains, which are assembled and maintained through epigenetic mechanisms. Extensive studies have focused on the assembly of heterochromatin at centromeres mediated by the RNA interference (RNAi) pathway. Recent studies, including ours, indicate that the exosome, an RNA quality control and surveillance complex, performs in a parallel pathway with RNAi to mediate epigenetic silencing. Although both RNAi and the exosome pathways are RNA-mediated and involved in processing long noncoding RNAs (ncRNAs) into small RNAs, exactly how the exosome pathway participates in heterochromatin assembly is not been demonstrated. Whether other RNAi-independent RNA processing pathways participate in epigenetic silencing is also unknown. We have recently identified a RNA-processing mechanism in epigenetic silencing that works independently of both RNAi and the exosome. The proposed research aims are designed to test the hypothesis that Dhp1, a conserved 5' to 3' exoribonuclease and ortholog of budding yeast Rat1 and metazoan Xrn2, plays a heretofore unknown role in epigenetic silencing, beyond its established role in transcription termination. Genetic, cell biology, and genomic approaches will be employed to investigate: 1) the localization of Dhp1 at heterochromatic regions; 2) Dhp1 binding proteins; and 3) the enzymatic activity of Dhp1 and potential co-activators in epigenetic silencing. Results will clarify how various RNA-processing pathways, acting together or independently, contribute to epigenetic regulation of the eukaryotic genome, a fundamental mechanism of gene expression. This study will be carried out in fission yeast, Schizosaccharomyces pombe (S. pombe), a premier model for studying epigenetic silencing because of its conserved epigenetic components and suitability for powerful combinatory experimental methods as well as undergraduate research. This project is significant and innovative. It will define a novel RNA-processing mechanism in epigenetic silencing that works independently of both RNAi and the exosome. Additionally, it will be the first exploration into how Dhp1/Rat1/Xrn2 functions in chromatin-based silencing.