 In this locus the CTCF protein regulates imprinted expression by binding to the unmethylated maternal imprinted control region (ICR) but not on the paternal ICR.When bound to the unmethylated maternal sequence, CTCF effectively blocks downstream enhancer elements from interacting with the "Igf2" gene promoter, leaving only the "H19" gene to be expressed.When insulator sequences are located in close proximity to the promoter of a gene, it has been suggested that they might serve to stabilize enhancer-promoter interactions.