Stereotyped p53 binding tuned by chromatin accessibility

We accessed the cell type specificity of p53 by directly measuring DNA binding in twelve cell lines in response to ionizing radiation. We find that that vast majority of binding sites are occupied across all cells lines uniformly, in contrast to p53 regulated gene expression which shows great diversity in the same context. We further identify a subset of p53 binding sites that are more restricted, appearing in one or a few cell lines. We find that chromatin accessibility explains much of these differential binding events. p53 DNA binding was measured in twelve cell lines after IR by ChIPseq. The transcriptional response of each of the twelve lines was also measured by mRNAseq. To explore the influence of chromatin accessability p53 binding was compared to ATAC-seq data from two cell lines.