Comparison of genotoxic vs. non-genotoxic stabilization of p53 provides insight into parallel stress-responsive transcriptional networks

The tumor suppressor protein p53 is activated in response to diverse intrinsic and extrinsic cellular stresses and controls a broad cell-protective gene network. Whether p53:DNA binding and subsequent transcriptional activation differs downstream of these diverse intrinsic and extrinsic activators within the same cell type is controversial. Using primary human fibroblasts, we assessed the genome-wide profile of p53 binding, chromatin structure, and transcriptional dynamics after either genotoxic or non-genotoxic activation of p53. Activation of p53 by treatment with either etoposide or the small molecule MDM2 inhibitor nutlin 3A yields strikingly similar genome-wide binding of p53 and concomitant changes to local chromatin modifications and structure. DNA damage, but not p53 activation per se , leads to increased expression of genes in an inflammatory cytokine pathway. Etoposide-mediated activation of this inflammation signature is inhibited by treatment with the NF-kB pathway inhibitor Bay 11-7082, but does not affect expression of canonical p53 target genes. Our data demonstrate that differential activation of p53 within the same cell type leads to highly similar genome-wide binding, chromatin dynamics, and gene expression dynamics, and that DNA damage-mediated signaling through NF-κB likely controls the observed pro-inflammatory cytokine gene expression pattern.