 CTCF protein is known to favourably bind to unmethylated sites, so it follows that methylation of CpG islands is a point of epigenetic regulation.An example of this is seen in the "Igf2-H19" imprinted locus where methylation of the paternal imprinted control region (ICR) prevents CTCF from binding.A second mechanism of regulation is through regulating proteins that are required for fully functioning CTCF insulators.