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Investigating the connection between aberrant R-loop formation and genome instability

研究异常 R 环形成与基因组不稳定性之间的联系

基本信息

批准号：
10750839
负责人：
Talysa C Viera
金额：
$ 6.95万
依托单位：
UNIVERSITY OF CALIFORNIA AT DAVIS
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-09-01 至 2025-08-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10750839
关键词：
Address Binding Bioinformatics Body Regions Cell model Cells Complex DNA DNA Damage DNA Double Strand Break DNA Structure Defect Disease Enzymes Excision Frequencies Future Gene Expression Gene Expression Process Genes Genetic Transcription Genome Genome Stability Genomic Instability Genomic approach Genomics Goals Hybrids Institution Intellectual functioning disability Knowledge Lead Link Maintenance Malignant Neoplasms Maps Measures Mediating Metabolism Molecular Nuclear Export Outcome Pancreatic ribonuclease Pathway interactions Pattern Phenotype Polymerase Process Promoter Regions RNA RNA Polymerase II RNA Processing Research Personnel Research Proposals Resolution Role Single-Stranded DNA Source Structure Testing Time Torpedo Transcript Work career gene conservation genome-wide genomic locus in vivo mRNA Precursor mammalian genome mutant nervous system disorder novel overexpression poly A specific exoribonuclease post-doctoral training promoter ribonuclease H1 skills transcription termination

项目摘要

Project Summary R-loops are non-B DNA structures that form co-transcriptionally upon reannealing of the nascent transcript to the DNA template strand, resulting in an RNA:DNA hybrid and a displaced single-strand of DNA. R-loops form dynamically over thousands of conserved genic loci in mammalian genomes under normal conditions. However, under conditions associated with dysfunctional RNA processing, “harmful” R-loops are thought to arise and contribute to DNA damage and genome instability phenotypes, resulting in cancer or neurological diseases. What differentiates normal and harmful R-loops remains unclear, and how harmful R-loops lead to DNA damage is not fully understood. Our group recently identified two classes of R-loops: Class I R-loops form during RNA polymerase II (RNAPII) promoter-proximal pausing at an elevated frequency, while Class II R-loops occur throughout gene bodies at moderate frequencies. Importantly, R-loop-associated genome instability phenotypes can be relieved by overexpression of RNase H1, an enzyme that specifically degrades RNA in RNA:DNA hybrids. The observation that RNase H1 primarily binds to promoter-proximal pause regions, and not gene body regions, implicates Class I R-loops as major drivers of genome instability. I hypothesize that Class I R-loops become elevated upon abnormal RNA processing, resulting in long-lasting paused RNAP polymerase II (RNAPII) complexes, transcription-replication conflicts, and DNA double-stranded breaks (DSBs) at promoter regions. To test this hypothesis, I will build upon a cellular model of defective RNA export by depleting THOC5, which is known to trigger R-loop-induced genomic instability and leverage integrative and unbiased genome- wide mapping approaches to directly measure perturbations in R-loop formation, nascent transcription, and DSB formation over time (Aim 1). I will overexpress (OE) RNase H1 in vivo and determine if it can suppress Class I R-loops, reduce paused RNAPII complexes, and lower DSBs (Aim 2). To further clarify the mechanism of genome stabilization by RNase H1 OE, I will investigate the possibility that RNase H1 activity permits the termination of paused RNAPII complexes via the XRN2 (5’-3’ exoribonuclease 2) “torpedo” pathway, thus relieving transcription-replication conflicts (Aim 3). I expect that this work will establish Class I R-loops associated with paused RNAPII complexes as a major class of genome-destabilizing obstacles, clarifying the identity of harmful R-loops and their impact on genomic stability. I also expect to reveal the molecular mechanism underlying the ability of RNase H1 to stabilize the genome, addressing largely ignored gaps in knowledge and highlighting novel roles for XRN2 in genome maintenance at promoter regions. Overall, this will fundamentally advance our understanding of the links between aberrant RNA processing, R-loop metabolism, and genome maintenance in the context of disease relevant processes, such as defects in RNA export associated with intellectual disabilities.

项目总结