Gamble, A.; Ward, T. A.; Wheeler, O. P.; Jones, C. M.; Bennett, L.; Vernon, E. G.; Thandendran, V.; Morris, J. P.; Ceppi, I.; Halder, S.; Borello, D.; Walker, T. D.; Rajan, J.; Dunphy, G.; Cejka, P.; Unterholzner, L.; Staples, C. J.

Replication stress is a key driver of DNA damage and genome instability. Replication stress-induced fork remodelling generates a new DNA end that is vulnerable to the action of nucleases, and which is protected by a range of factors including the canonical tumour suppressors BRCA1 and BRCA2. Here we report that replication stress drives elevated production of cytokines and chemokines in the absence of DNA damage. The DNA sensor IFI16 binds nascent DNA at stalled replication forks and signals via the DNA sensing adaptor STING, to induce the activation of NF-{kappa}B and the production of pro-inflammatory cytokines in response to replication stress. IFI16 also acts directly at stalled replication forks to protect nascent DNA from degradation by the nucleases MRE11 and DNA2. Furthermore, IFI16 is required for the interferon-mediated rescue of fork protection in BRCA-deficient cells, highlighting the critical role of IFI16 in the cross-talk between innate immunity and fork protection during replication stress.