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

项目总结： 核RNAi是一条进化保守的途径，由小干扰RNA(SiRNAs)引导 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“非我”DNA。自发现以来，核RNAi提供了一个强大的范式 研究RNA介导的染色质调节和跨代表观遗传。在线虫中，核 RNAi和可遗传沉默可以通过给蠕虫喂食外源dsRNA靶向来方便地触发 一种原生基因。这种方法的补充是通过研究发生在内源性 线虫基因组中的靶标。使用这个独特的易处理系统，我们过去发表的作品 Funding Cycle有了以下发现，也提出了新的问题：(1)异染色质 在维持阶段，Mark H3K9me3在功能上可以与转录沉默分离。 H3K9me3非依赖转录抑制机制是什么？(2)异染色质酶 SET-32对于RNAi的建立阶段是必需的，但对于RNAi的维护阶段是必不可少的。何以 SET-32促进沉默建立？(3)内源性靶基因在以下基因的子集中瞬时表达 野生型成年动物生殖细胞处于增殖和早期减数分裂阶段。这是一种什么机制 低水平转录的发育调节，以及它如何有助于增强 表观遗传沉默记忆？(4)当我们去沉默核RNAi的内源性靶标时，它们的转录本 富含生殖系细胞核。这种核定位在触发RNAi方面的意义是什么？在 建议的新资金周期，我们将采用新的和已建立的遗传、生化、细胞生物学和 通过实现以下目标，采用计算方法来回答这些问题。(1)调查 沉默建立的跨世代表观遗传机制。(2)鉴定一种新的组蛋白 修饰，H3K23me3，及其在生殖系核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，探索基础但尚未绘制的地图 现代生物学的领地，将促进我们对RNA-染色质相互作用、遗传的理解 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.