 The human genome contains anywhere between 15,000-40,000 CTCF binding sites depending on cell type, suggesting a widespread role for CTCF in gene regulation.In addition CTCF binding sites act as nucleosome positioning anchors so that, when used to align various genomic signals, multiple flanking nucleosomes can be readily identified.On the other hand, high-resolution nucleosome mapping studies have demonstrated that the differences of CTCF binding between cell types may be attributed to the differences in nucleosome locations.