Chromatin immunoprecipitations were performed with cross-linked chromatin from 4 x 10 6 HeLa cells and either 10 μl of CTCF (D1A7) XP ® 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 human c-Myc promoter primers, SimpleChIP ® Human H19/Igf2 ICR Primers #5172, 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.