Chromatin immunoprecipitations were performed with cross-linked chromatin from 4x10e6 HeLa cells and either 10ul of Tri-Methyl-Histone H4 (Lys20) Rabbit mAb, or 2ul of Normal Rabbit IgG using SimpleChIP Enzymatic Chromatin IP Kit (Magnetic Beads). The enriched DNA was quantified by real-time PCR using SimpleChIP Human a Satellite Repeat Primers, SimpleChIP Human AFM Intron 1 Primers and SimpleChIP Human GAPDH Exon 1 Primers. The amount of immunoprecipitated DNA in each sample is represented as signal relative to the total amount of input chromatin, which is equivalent to one.