DDX18 prevents R-loop-induced DNA damage and genome instability via PARP-1

Highlights•The helicase DDX18 mediates homeostasis of the DNA:RNA hybrids known as R loops•The function of DDX18 in R-loop homeostasis is dependent on PARP-1•DDX18 C terminus is required for poly(ADP-ribose) chain interaction at DNA-damage sites•DDX18 mediates R-loop-induced DNA damage and genome integritySummaryR 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.Graphical abstract