Cell
Volume 98, Issue 3, 6 August 1999, Pages 387-396
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Article
The Protein CTCF Is Required for the Enhancer Blocking Activity of Vertebrate Insulators

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Abstract

An insulator is a DNA sequence that can act as a barrier to the influences of neighboring cis-acting elements, preventing gene activation, for example, when located between an enhancer and a promoter. We have identified a 42 bp fragment of the chicken β-globin insulator that is both necessary and sufficient for enhancer blocking activity in human cells. We show that this sequence is the binding site for CTCF, a previously identified eleven–zinc finger DNA-binding protein that is highly conserved in vertebrates. CTCF sites are present in all of the vertebrate enhancer-blocking elements we have examined. We suggest that directional enhancer blocking by CTCF is a conserved component of gene regulation in vertebrates.

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