Analysis of p53 binding to head-to-tail response element using chromatin immunoprecipitation assays.

<p>MCF10A, MCF10A/OD, and MCF10A/Δp53 cells were incubated with either fresh media (untreated) or 10 ng/ml SN38 for 24 hours, followed by cross-linking in 1% formaldehyde. Chromatin was then purified, sonicated, and immunoprecipitated with anti-p53 antibody or negative IgG antibody. Unprecipitated chromatin was used as a positive control (input). DNA was isolated and amplified by PCR using primers flanking the head-to-tail response element in the cyclin B promoter or the RNA Polymerase II binding site from the GAPDH promoter. The amplified PCR fragments were analyzed by agarose gel electrophoresis.