Figure 1. Schematic representation of the imprinted H19 locus and TRIM28/ZFP57 complex binding to the ICR. (A) Gene expression from the H19 imprinted locus is controlled by an enhancer, whose activity is directed to the H19 promoter by binding the insulator CTCF to the unmethylated ICR on the maternal allele. Methylation of the ICR on the paternal allele prevents CTCF binding, thus directing the enhancer activity to the Igf2/Igf2as promoters. (B) The ICR of the H19 locus contains a ZFP57 binding site. ZFP57 binds DNA in a sequence- and methylation-dependent manner, attracting TRIM28 and several chromatin and DNA modifying components.