RNA-mediated Chromatin Regulation and Epigenetic Inheritance in C. elegans

项目概要： 核RNAi是一种进化上保守的途径，其中小干扰RNA（siRNAs）引导细胞内的RNA干扰。 染色质修饰和转录抑制。它通过表观遗传沉默来保护宿主基因组 转座子和其他“非自我”DNA。自发现以来，核RNAi提供了一个强大的范例， 研究RNA介导染色质调节和跨代表观遗传。In C.秀丽线虫，核的 RNAi和遗传沉默可以通过用外源dsRNA靶向喂养蠕虫而方便地触发 一种天然基因这种方法是补充调查分子事件发生在内源性 目标在C。线虫基因组使用这个独特的易处理的系统，我们过去发表的作品 研究人员在研究中取得了以下发现，同时也提出了新的问题：（1）异染色质 标记H3 K9 me 3可以在维持期与转录沉默功能性地解耦。 什么是H3 K9 me 3非依赖性转录抑制机制？(2)异染色质酶 SET-32在RNAi的建立阶段是必需的，但在维持阶段是必需的。如何 SET-32促进沉默建立？(3)内源性靶标在一个亚组中瞬时表达， 在野生型成年动物中，生殖细胞处于增殖和早期减数分裂阶段。这是什么机制 低水平转录的发育调控，以及它如何有助于加强 表观遗传沉默记忆(4)当我们去沉默核RNAi的内源性靶点时， 都富含生殖细胞核。这种核定位在触发RNAi中的意义是什么？在 建议新的资金周期，我们将采取新的和建立遗传，生物化学，细胞生物学， 计算方法通过实现以下目标来回答这些问题。(1)探讨 沉默建立的跨代表观遗传机制。(2)表征一种新的组蛋白 修饰，H3 K23 me 3及其在生殖细胞核RNAi中的作用。(3)确定触发机制， 核RNAi的内源性靶点。拟议的研究，探索基本的，但未映射 现代生物学领域，将促进我们对RNA-染色质相互作用，遗传 表观遗传状态和基因组监测，这些都与人类发育和疾病有关。

PROJECT SUMMARY: Nuclear RNAi is an evolutionarily conserved pathway in which small interfering RNAs (siRNAs) guide chromatin modifications and transcriptional repression. It protects the host genome by epigenetically silencing transposons and other “non-self” DNA. Since its discovery, nuclear RNAi has provided a powerful paradigm to study RNA-mediated chromatin regulation and transgenerational epigenetic inheritance. In C. elegans, nuclear RNAi and heritable silencing can be conveniently triggered by feeding worms with exogenous dsRNA targeting a native gene. This approach is complemented by investigating molecular events occurring at the endogenous targets in the C. elegans genome. Using this uniquely tractable system, our published works done in the past funding cycle have made the following discoveries, which also raised new questions: (1) The heterochromatin mark H3K9me3 can be functionally decoupled from transcriptional silencing during the maintenance phase. What is the H3K9me3-independent transcriptional repression mechanism? (2) The heterochromatin enzyme SET-32 is required for the establishment phase but dispensable for the maintenance phase of RNAi. How does SET-32 promote silencing establishment? (3) Endogenous targets are transiently expressed in a subset of germ cells at the proliferation and early meiotic stage in wild type adult animals. What is the mechanism of the developmental regulation of the low level transcription, and how does it contribute to the reinforcement of epigenetic silencing memory? (4) When we de-silence endogenous targets of nuclear RNAi, their transcripts are enriched in germline nuclei. What is the significance of this nuclear localization in triggering RNAi? In the proposed new funding cycle, we will take both novel and established genetic, biochemical, cell biology, and computational approaches to answer these questions by achieving the following aims. (1) Investigate the transgenerational epigenetic mechanisms of silencing establishment. (2) Characterize a novel histone modification, H3K23me3, and its role in germline nuclear RNAi. (3) Determine the triggering mechanisms at the endogenous target of nuclear RNAi. The proposed studies, which explore fundamental yet unmapped territory of modern biology, will advance our understanding of RNA-chromatin interaction, inheritance of epigenetic states, and genome surveillance, which are all relevant to human development and disease.