|Title||CTCF mediates methylation-sensitive enhancer-blocking activity at the H19/Igf2 locus.|
|Publication Type||Journal Article|
|Year of Publication||2000|
|Authors||Hark, AT, Schoenherr, CJ, Katz, DJ, Ingram, RS, Levorse, JM, Tilghman, SM|
|Date Published||2000 May 25|
|Keywords||Animals, 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.