Chromatin immunoprecipitations were performed with cross-linked chromatin from 4 x 10 6 HeLa cells and either 10 μl of Tri-Methyl-Histone H4 (Lys20) (D84D2) Rabbit mAb, or 2 μl of Normal Rabbit IgG #2729, using SimpleChIP ® Enzymatic Chromatin IP Kit (Magnetic Beads) #9003. The enriched DNA was quantified by real-time PCR using SimpleChIP ® Human α Satellite Repeat Primers #4486, SimpleChIP ® Human AFM Intron 1 Primers #5098, and SimpleChIP ® Human GAPDH Exon 1 Primers #5516. 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.