BRCA2 promotes DNA-RNA hybrid resolution by DDX5 helicase at DNA breaks to facilitate their repair

The BRCA2 tumor suppressor is a DNA double-strand break repair factor essential to maintain genome integrity. BRCA2-deficient cells spontaneously accumulate DNA-RNA hybrids, a known source of genome instability. However, the specific role of BRCA2 on these structures remains poorly understood. Here we identified the DEAD-box RNA helicase DDX5 as a BRCA2 interacting partner. We show that DDX5 associates with DNA-RNA hybrids that form in the vicinity of DSBs and this association is enhanced by BRCA2. Notably, BRCA2 stimulates the DNA-RNA hybrid helicase activity of DDX5. Impaired BRCA2-DDX5 interaction, as observed in cells bearing the breast cancer variant BRCA2-T207A, reduces DDX5 association with DSBs, decreases the number of RPA foci upon irradiation and impairs RAD51 repair foci formation. Our findings are consistent with DNA-RNA hybrids being an impediment for the repair of DSBs by homologous recombination and reveal BRCA2 and DDX5 as active players in their removal. Genome-wide inspection of RNA-DNA hybrids accumulation in siC control and DDX5-depleted (siDDX5) K562 cells