ChIP assays were performed using HeLa cells treated with colcemid, the antibody against H3K9me3S10p (bs-53072R) and optimized PCR primer sets for qPCR. ChIP was performed using sheared chromatin from 10,000 cells per IP. A titration of the antibody consisting of 1, 5, and 10 μl per ChIP experiment was analyzed. Additionally, the same titration was analyzed after incubation of the antibody with 5 nmol blocking peptide (cat. No. sp-128-050) for 1 hour at room temperature. IgG (5 μg/IP) was used as negative IP control. QPCR was performed with primers for the promoter of the active genes GAPDH and c-fos and for the heterochromatin marker Sat2. The figure shows the recovery, expressed as a % of input (the relative amount of immunoprecipitated DNA compared to input DNA after qPCR analysis).