DNA damage-induced cytotoxicity is mediated by the cooperative interaction of phospho-NF-κB p50 and a single nucleotide in the κB-site

Phosphorylation of the NF-kappa B subunit, p50, is necessary for cytotoxicity in response to DNA methylation damage. Here, we demonstrate that serine 329 phosphorylation regulates the interaction of p50 with specific NF-kappa B binding elements based on the identity of a single kappa B-site nucleotide. Specifically, S329 phosphorylation reduces the affinity of p50 for kappa B-sites that have a cytosine (C) at the -1 position without affecting binding to sequences with a -1 adenine. The differential interaction between phospho-p50 and the -1 base regulates the downstream transcriptional response and underlies the inhibition of anti-apoptotic gene expression following DNA damage. In genes with multiple kappa B-sites, the presence of a single -1C kappa B-site enables inhibition of NF-kappa B-dependent activity. The data suggest that interaction between phospho-p50 and the -1 kappa B nucleotide facilitates cytotoxicity in response to DNA damage. Moreover, although conservation of the entire kappa B-site sequence is not seen across species, the identity of the -1 nt in critical anti-apoptotic genes is conserved such that the overall response to DNA damage is maintained.