Impact of DNA methylation on cell-selective CTCF binding. (A) Example CTCF binding sites, where occupancy (above) quantitatively increases as local CpG methylation decreases (below). Green indicates CpG is 0% methylated; yellow, 50%; and red, 100%. (B) Quantitative analysis of methylation at the boxed CTCF binding site in A. (C) Global impact of methylation at variable CTCF sites monitored by RRBS. Sixty-five percent of sites with cell-type selective patterns of methylation also exhibited differences in occupancy. (D) At methylated binding sites, occupancy was reduced on average by 87% compared with cell lines without methylation at the same site. Shown are sites where increased methylation was associated with decreased occupancy (98% of all significant sites).
