TitleCTCF mediates methylation-sensitive enhancer-blocking activity at the H19/Igf2 locus.
Publication TypeJournal Article
Year of Publication2000
AuthorsHark, AT, Schoenherr, CJ, Katz, DJ, Ingram, RS, Levorse, JM, Tilghman, SM
Date Published2000 May 25
KeywordsAnimals, Cell Line, DNA, DNA Methylation, DNA-Binding Proteins, Enhancer Elements, Genetic, Gene Expression Regulation, Genomic Imprinting, Humans, Insulin-Like Growth Factor II, Mice, Mice, Transgenic, Muscle Proteins, Protein Binding, Regulatory Sequences, Nucleic Acid, Repressor Proteins, RNA, Long Noncoding, RNA, Untranslated, Transcription Factors, Zinc Fingers

The Insulin-like growth factor 2 (Igf2) and H19 genes are imprinted, resulting in silencing of the maternal and paternal alleles, respectively. This event is dependent upon an imprinted-control region two kilobases upstream of H19 (refs 1, 2). On the paternal chromosome this element is methylated and required for the silencing of H19 (refs 2-4). On the maternal chromosome the region is unmethylated and required for silencing of the Igf2 gene 90 kilobases upstream. We have proposed that the unmethylated imprinted-control region acts as a chromatin boundary that blocks the interaction of Igf2 with enhancers that lie 3' of H19 (refs 5, 6). This enhancer-blocking activity would then be lost when the region was methylated, thereby allowing expression of Igf2 paternally. Here we show, using transgenic mice and tissue culture, that the unmethylated imprinted-control regions from mouse and human H19 exhibit enhancer-blocking activity. Furthermore, we show that CTCF, a zinc finger protein implicated in vertebrate boundary function, binds to several sites in the unmethylated imprinted-control region that are essential for enhancer blocking. Consistent with our model, CTCF binding is abolished by DNA methylation. This is the first example, to our knowledge, of a regulated chromatin boundary in vertebrates.

Alternate JournalNature