Chromatin immunoprecipitations were performed with cross-linked chromatin from 4 x 10 6 MCF7 cells grown in phenol red free medium and 5% charcoal stripped FBS for 4 d then treated with β-estradiol (10 nM) for 45 min and either 10 μl of COBRA1 (D6K9A) 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 c-Myc Intron 1 Primers #14905, human PMAIP1 promoter primers, and SimpleChIP ® Human α Satellite Repeat Primers #4486. 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.