NEMO is essential for directing IKKα and ATM to the sites of DNA damage

We previously demonstrated that IKKα binds to and phosphorylates ATM thus potentiating the non-homologous end joining DNA damage repair pathway in cancer cells. Hence, inhibiting IKKα enhances the efficacy of DNA damage-based anticancer therapy. Whether additional elements contribute to this resistance-related mechanism remains unknown. We here show that NEMO physically interacts with the ATM-IKKα complex before damage. Upon exposure to damaging agents, NEMO is dispensable for ATM activation, but it is required to drive active ATM and IKKα to the sites of damage thus enabling DNA damage resolution. Recognition of damaged DNA by this IKKα/NEMO/ATM complex is partially mediated by direct interaction of NEMO to histones but highly dependent on PARP1 activity. Finally, we detected increased ATR activity in NEMO-deficient cells, and that ATR inhibition potentiates the effect of chemotherapy upon NEMO or IKKα depletion. Bioinformatic analysis of public CRC datasets support the functional impact of the IKKα/NEMO/ATM pathway in patient prognosis, which could be therapeutically exploited.