ChIP assays were performed using HeLa cells, H3K9ac Polyclonal Antibody (Cat. No. bs-53092R) and optimized PCR primer pairs for qPCR. ChIP was performed with a ChIP-seq kit, using sheared chromatin from 1 million cells. A titration consisting of 1, 2, 5 and 10 μg of antibody per ChIP experiment was analyzed. IgG (2 μg/IP) was used as a negative IP control. Quantitative PCR was performed with primers specific for the promoter of the active genes GAPDH and EIF4A2, used as positive controls, and for exon 2 of the inactive myoglobin (MB) gene and the Sat2 satellite repeat, used as negative controls. The figure shows the recovery, expressed as a % of input (the relative amount of immunoprecipitated DNA compared to input DNA after qPCR analysis). These results are in accordance with the observation that acetylation of K9 at histone H3 is associated with the promoters of active genes.