HELZ is a RNA-DNA helicase that resolves R loops to facilitate homologous recombination repair

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Abstract
R loop homeostasis is critical for DNA double-strand break (DSB) repair; however, how R loops are resolved in this context is poorly understood. Here, we define HELZ as a unique RNA-DNA helicase that resolves R loops to facilitate homologous recombination (HR) repair. From a synthetic lethal etoposide resistance siRNA screen, we found that HELZ depletion causes R loop-mediated hypersensitivity to DSB-inducing agents, and HELZ localizes and binds to DSBs. HELZ preferentially binds to and unwinds RNA-DNA hybrids with 5’ssRNA overhangs to promote R loop resolution genome-wide and at DSBs. Interestingly, HELZ facilitates BRCA1 recruitment to DSBs by preventing R loop accumulation, thereby promoting DNA end resection and HR to prevent R loop mediated genomic instability. In summary, we show that HELZ resolves R loops critical for HR, thereby promoting genome stability and resistance to DSB-inducing agents.
Funding Information
  • National Cancer Institute (R01CA178999)
  • National Cancer Institute (R01CA254403)
  • National Cancer Institute (U54CA274513)
  • National Cancer Institute (R01CA301614)

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