ChIP assays were performed using HeLa cells treated with colcemid, the H3K27me3S28p antibody (bs-53053R) and optimized PCR primer pairs for qPCR. ChIP was performed using sheared chromatin from 10,000 cells. A titration of the antibody consisting of 1, 5 and 10 μl per ChIP experiment was analysed. Additionally, ChIP was performed after incubation of the antibody with 5 nmol blocking peptide (cat. No. sp-091-050) for 1 hour at room temperature. IgG (5 μg/IP) was used as negative IP control. QPCR was performed with primers for the promoters of the active genes c-fos and RPL30 and for the inactive gene MYOD. The figure shows the recovery, expressed as a % of input (the relative amount of immunoprecipitated DNA compared to input DNA after qPCR analysis).