In brief, cells were crosslinked with 1% formaldehyde, glycine quenched, lysed with cell lysis buffer (Sigma, #2978) supplemented with 1 mM PMSF, and subjected to pulse sonication (20s with 30s internal, 5 cycles). The supernatant was then immunoprecipitated with the p53 and rabbit IgG antibodies (Cell Signaling, #9282 and #2729) at 4°C overnight and incubated with Magna ChIP Protein G magnetic beads (Millipore, #16-662). Libraries were prepared according to Illumina's instructions accompanying the DNA Sample Kit (Part# 0801-0303). Briefly, DNA was end-repaired using a combination of T4 DNA polymerase, E. coli DNA Pol I large fragment (Klenow polymerase) and T4 polynucleotide kinase. The blunt, phosphorylated ends were treated with Klenow fragment (32 to 52 exo minus) and dATP to yield a protruding 3- 'A' base for ligation of Illumina's adapters which have a single 'T' base overhang at the 3' end. After adapter ligation DNA was PCR amplified with Illumina primers for 15 cycles and library fragments of ~250 bp (insert plus adaptor and PCR primer sequences) were band isolated from an agarose gel. The purified DNA was captured on an Illumina flow cell for cluster generation. Libraries were sequenced on the Illumina HiSeq following the manufacturer's protocols.