Genome-wide analysis of p53-regulated transcription in Myc-driven lymphomas

The tumour suppressor p53 is a transcription factor that controls cellular stress responses. Here, we dissected the transcriptional programmes triggered upon restoration of p53 in Myc-driven lymphomas, based on the integrated analysis of p53 genomic occupancy and gene regulation. p53 binding sites were identified at promoters and enhancers, both characterized by the pre-existence of active chromatin marks. Only a small fraction of these sites showed the 20 base-pair p53 consensus motif, suggesting that p53 recruitment to genomic DNA was primarily mediated through protein-protein interactions in a chromatin context. p53 also targeted distal sites devoid of activation marks, at which binding was prevalently driven by sequence recognition. In all instances, the relevant motif was the canonical unsplit consensus element, with no clear evidence for p53 recruitment by split motifs. At promoters, p53 binding to the consensus motif was associated with gene induction, but not repression, indicating that the latter was most likely indirect. Altogether, our data highlight key features of genome recognition by p53 and provide unprecedented insight into the pathways associated with p53 reactivation and tumour regression, paving the way for their therapeutic application.