Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA; Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
Cell Rep. 2022 Jul 19;40(3):111089. doi: 10.1016/j.celrep.2022.111089.
R loops occur frequently in genomes and contribute to fundamental biological processes at multiple levels. Consequently, understanding the molecular and cellular biology of R loops has become an emerging area of research. Here, it is shown that poly(ADP-ribose) polymerase-1 (PARP-1) can mediate the association of DDX18, a putative RNA helicase, with R loops thereby modulating R-loop homeostasis in endogenous R-loop-prone and DNA lesion regions. DDX18 depletion results in aberrant endogenous R-loop accumulation, which leads to DNA-replication defects. In addition, DDX18 depletion renders cells more sensitive to DNA-damaging agents and reduces RPA32 and RAD51 foci formation in response to irradiation. Notably, DDX18 depletion leads to γH2AX accumulation and genome instability, and RNase H1 overexpression rescues all the DNA-repair defects caused by DDX18 depletion. Taken together, these studies uncover a function of DDX18 in R-loop-mediated events and suggest a role for PARP-1 in mediating the binding of specific DDX-family proteins with R loops in cells.
R 环在基因组中频繁出现，并在多个层面上为基础的生物学过程做出贡献。因此，理解 R 环的分子和细胞生物学已经成为一个新兴的研究领域。在这里，研究表明多聚（ADP-核糖）聚合酶-1（PARP-1）可以介导假定的 RNA 解旋酶 DDX18 与 R 环的关联，从而调节内源性 R 环倾向和 DNA 损伤区域的 R 环稳态。DDX18 的耗竭导致异常的内源性 R 环积累，从而导致 DNA 复制缺陷。此外，DDX18 的耗竭使细胞对 DNA 损伤剂更敏感，并减少 RPA32 和 RAD51 焦点形成对辐照的反应。值得注意的是，DDX18 的耗竭导致 γH2AX 积累和基因组不稳定性，而 RNase H1 的过表达挽救了 DDX18 耗竭引起的所有 DNA 修复缺陷。总之，这些研究揭示了 DDX18 在 R 环介导的事件中的作用，并表明 PARP-1 在介导特定 DDX 家族蛋白与细胞中 R 环的结合中发挥作用。
