HELZ promotes R loop resolution to facilitate DNA double-strand break repair by homologous recombination

Successful R-loop homeostasis consists of its timely biogenesis and removal throughout the genome to regulate diverse cellular processes. Yet, they are considered hazardous source to our genome when their turnover goes awry. Here, we report HELZ, a novel player in R-loop homeostasis and DNA repair pathway. HELZ mediates resistance to several DNA damaging agents, and localizes to DSBs and its depletion increases R-loops fostering genomic instability. Loss of HELZ results in impaired homologous recombination (HR) due to R-loops accumulation, with an increase in classical-non-homologous end joining (c-NHEJ), suggesting a role for HELZ in regulating DSB repair pathway choice. Rad51 retention at DSBs is governed by HELZ mediated R-loop accumulation. Mechanistically, our data show that HELZ complexes with BRCA1 and facilitates its recruitment to DSBs in an R-loop dependent manner. Collectively, our data support a model in which HELZ recruits BRCA1 and facilitates R loop resolution at DSBs to promote HR and therefore maintains genome stability. R-loop profiles of HELZ knockdown U2OS cells