Histone acetylation at 41BBL promoters in non-radiated and irradiated cells. ChIP assays were carried out in non-irradiated, irradiated (10 Gy), and TSA-treated (500 nM) HCT116 cells. Following 48 h of TSA treatment, lysates were immunoprecipitated with control antibody or with anti-acetyl histone H3. Associated DNA was isolated and analyzed via real time PCR using primers spanning the 41BBL, GAPDH and CIITA promoters. Real-time PCR values were normalized to the total amount of promoter DNA added (input). Input values represent 5% of the total cell lysate. Values represent mean ± SEM of three independent experiments. **P < 0.005. A. Global levels of Histone H3 acetylation associated with the 41BBL promoter. B. Global levels of Histone H3 acetylation associated with the GAPDH promoter. C. Global levels of acetylated Histone H3 associated with the CIITA promoter.