ATRA/FK228 increase H4 and H3-Lys9 acetylation in the MDR1 promoter (CCAAT region) in NB4 cells. (A) The data shown are derived from TaqMan PCR analyses of ChIP assays, as described in “Chromatin immunoprecipitation assay.” Chromatin from NB4 cells treated with ATRA (1.0 μM) and/or FK228 (3.0 nM) for 24 hours was immunoprecipitated with an antibody against acetylated H4 (i) and H3-Lys9 (ii) and analyzed by TaqMan PCR using probes and primers corresponding to the MDR1 promoter (CCAAT region). The graph shows the mean ± SD of representative data from 3 independent ChIP assays. A statistically significant difference was determined by ANOVA and Fisher post hoc tests (^**P < .05). (B) Real-time TaqMan PCR profiles of MDR1 promoter (CCAAT region) amplification shown by examples of ChIP assays. (i) The input curve shows the total genomic DNA before immunoprecipitation. The negative control curve shows the results of chromatin immunoprecipitations using PBS. Representative profiles of acetylated H4 (ii) and H3-Lys9 (iii) are shown by examples. (iv-vi) Real-time TaqMan PCR profiles of ANXA1 promoter amplification in the same sample of subpanels i-iii shown as a negative control for ChIP assays. (iv) Input and negative control, (v) acetylated H4, (vi) acetylated H3-Lys9.