Recruitment of RBM6 to DNA double-strand breaks fosters homologous recombination repair

DNA double-strand breaks (DSBs) are highly toxic lesions that threaten genome integrity and cell survival. To avoid harmful repercussions of DSBs, a wide variety of DNA repair factors are recruited to execute DSB repair by either non-homologous end joining (NHEJ), homologous recombination (HR), or alternative end-joining pathways. Previously, we demonstrated that RBM6 splicing factor facilitates HR of DSB by regulating alternative splicing-coupled nonstop- decay of the HR protein APBB1/Fe65. Here, we describe a splicing-independent function of RBM6 in promoting HR repair of DSBs. We show that RBM6 is rapidly and transiently recruited to DSB sites in a PARP1-dependent manner. Furthermore, we demonstrate that RBM6 doesn’t undergo ADP-ribosylation nor binds poly (ADP-ribose) moieties, suggesting that PARP1 activity indirectly regulates RBM6 recruitment to DNA breakage sites. Deletion mapping analysis revealed a region containing 5 glycine residues within the G-patch domain that regulates RBM6 accumulation at DNA damage sites. We further ascertain that RBM6 interacts with Rad51, and this interaction is attenuated in RBM6 mutant lacking the G-patch domain (RBM6 del(G-patch) ). Consequently, RBM6 del(G-patch) cells exhibit reduced levels of Rad51 foci after ionizing radiation as compared to control cells. In addition, while RBM6 deletion mutant lacking the G-patch domain has no detectable effect on the expression levels of its splicing targets Fe65 and Eya2, it fails to restore the integrity of HR. Altogether, our results suggest that RBM6 recruitment to DSB promotes HR repair, irrespective of its splicing activity.