Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, UK.
Nat Commun. 2021 Jun 22;12(1):3849. doi: 10.1038/s41467-021-24201-w.
DNA-RNA hybrid structures have been detected at the vicinity of DNA double-strand breaks (DSBs) occurring within transcriptional active regions of the genome. The induction of DNA-RNA hybrids strongly affects the repair of these DSBs, but the nature of these structures and how they are formed remain poorly understood. Here we provide evidence that R loops, three-stranded structures containing DNA-RNA hybrids and the displaced single-stranded DNA (ssDNA) can form at sub-telomeric DSBs. These R loops are generated independently of DNA resection but are induced alongside two-stranded DNA-RNA hybrids that form on ssDNA generated by DNA resection. We further identified UPF1, an RNA/DNA helicase, as a crucial factor that drives the formation of these R loops and DNA-RNA hybrids to stimulate DNA resection, homologous recombination, microhomology-mediated end joining and DNA damage checkpoint activation. Our data show that R loops and DNA-RNA hybrids are actively generated at DSBs to facilitate DNA repair.
DNA-RNA 杂交结构已在基因组转录活跃区域内发生的 DNA 双链断裂 (DSB) 附近检测到。DNA-RNA 杂交的诱导强烈影响这些 DSB 的修复，但这些结构的性质以及它们是如何形成的仍知之甚少。在这里，我们提供的证据表明，含有 DNA-RNA 杂交和置换单链 DNA（ssDNA）的三链结构 R 环可以在亚端粒 DSB 处形成。这些 R 环的形成不依赖于 DNA 切除，但与由 DNA 切除产生的 ssDNA 上形成的双链 DNA-RNA 杂交物一起诱导。我们进一步鉴定了 RNA/DNA 解旋酶 UPF1，作为驱动这些 R 环和 DNA-RNA 杂交形成以刺激 DNA 切除、同源重组、微同源介导的末端连接和 DNA 损伤检查点激活的关键因素。我们的数据表明，R 环和 DNA-RNA 杂交物在 DSB 处被积极生成，以促进 DNA 修复。
