Nono stimulates the DNA damage response by mediating the induction of Gadd45b [RNA-seq]

RNA-binding proteins (RBPs) are frequently deregulated in cancer and emerge as effectors of the DNA damage response (DDR). The non-POU domain-containing octamer-binding protein NONO/p54nrb is a multi-functional RBP that modulates the production and processing of mRNA in unperturbed cells, but also promotes the repair of DNA double-strand breaks (DSBs). Here, we investigate the impact of Nono deletion in the murine cell-based lung cancer model KP (KRasG12D, Trp53-/-). We show that the deletion of Nono impairs the response to DSBs induced by the topoisomerase-II inhibitor etoposide. Nono-deficient KP (KPN) cells display prolonged activation of DSB signaling and an increased amount of DSBs. The defects in the DDR are accompanied with reduced RNAPII promoter occupancy, elevated levels of DNA-RNA-hybrids (R-loops), and attenuated induction of the DDR factor growth arrest and DNA damage inducible beta (Gadd45b). Our data suggest a Nono-mediated, genome-protective crosstalk of the DDR with the RNA metabolism. Our data characterise Gadd45b as putative Nono-dependent effector of the DDR and suggest that Nono mediates a genome-protective crosstalk of the DDR with the RNA metabolism via induction of Gadd45b.