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RNA Interference and Heterochromatic Silencing in Replication and Quiescence

复制和静止过程中的 RNA 干扰和异染色质沉默

基本信息

批准号：
10677770
负责人：
ROBERT A MARTIENSSEN
金额：
$ 43.51万
依托单位：
COLD SPRING HARBOR LABORATORY
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-08-05 至 2027-07-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10677770
关键词：
Autoimmune Diseases Biological Models Bromodomain Caenorhabditis elegans Cell Cycle Chromosomal Stability Chromosome Segregation Chromosomes DNA DNA Damage DNA Repair DNA replication fork Disease Drosophila genus Epigenetic Process Event Fission Yeast Gene Expression Regulation Gene Silencing Genetic Screening Genetic Transcription Genome Stability Genomic Instability Goals Health Heterochromatin Hybrids Link Liquid substance Malignant Neoplasms Mammalian Cell Mediating MicroRNAs Mus Mutant Strains Mice Pathway interactions Phase Phase Transition Polymerase Post-Transcriptional Regulation Property RNA RNA Interference RNA Polymerase II Repetitive Sequence Research Ribonuclease H Role S phase Structure System Transcription Coactivator Ubiquitin Untranslated RNA Work Yeasts embryonic stem cell epigenetic silencing genome integrity heterochromatin-specific nonhistone chromosomal protein HP-1 histone methylation histone modification homologous recombination mutant novel piRNA prevent recruit repaired stem cell model targeted treatment ubiquitin ligase

项目摘要

Gene regulation by RNA interference is usually attributed to microRNA, but RNAi has a more ancient and fundamental role in heterochromatic silencing and genome stability. Heterochromatin comprises condensed repetitive regions of eukaryotic chromosomes, and mediates transcriptional silencing, chromosome segregation and genome integrity. We have found that heterochromatin is unexpectedly transcribed, and that subsequent RNAi guides histone modification. In the fission yeast S. pombe, “co- transcriptional” silencing occurs during the S phase of the cell cycle, followed by transcriptional silencing thereafter. Release of RNA polymerase II (Pol II) during replication prevents DNA damage, but without RNAi, replication forks stall and are repaired by homologous recombination (HR), causing genome instability. We have found that RNAi regulates genome stability through R-loops, RNA-DNA hybrid structures at transcription-replication collisions that promote HR. Silencing depends on histone modification, but recent studies show this may be an oversimplification. First, histone methylation recruits Heterochromatin Protein 1, which mediates liquid-liquid phase separation (LLPS) and may limit access to Pol II. Second, RNAi also recruits ubiquitin ligase, and we recently found that ubiquitin promotes these phase transitions. RNAi guides histone modification in C. elegans and Drosophila, but conservation in mammalian systems has been controversial. For example, piRNAs mediate histone modification in the germline but do not depend on Dicer, while genome instability in Dicer mutant mouse embryonic stem cells (mESC) depends on transcription of satellite repeats. Strikingly, we have found genome instability in Dicer-/- mESC depends on the transcriptional co- activator BRD4, and identical in-frame bromodomain deletions rescue Dicer mutants in fission yeast. S. pombe is an outstanding model system for cell cycle research, and we were the first to show that RNAi is essential for quiescence (G0). Genetic screens have revealed that nucleolar RNA silencing and histone modifications mediate this novel function. Our goals in the next five years are to determine the elusive mechanism by which RNAi guides each aspect of heterochromatin from repeat instability, to silencing, chromosome segregation and DNA repair as well as survival in quiescence. Our recent work suggests a central role for long non-coding RNA, R-loops and the activity of RNAse H in the upstream steps in this pathway. Downstream events include histone modification and LLPS that may underlie the classically “condensed” properties of heterochromatin. We will use our stem cell model to assess the conservation and relevance of these mechanisms in health and disease, especially in cancer.

基因受RNA干扰的调控通常归因于microRNA，但RNAi具有更古老的机制