Tandem CTCF sites function as insulators to balance spatial chromatin contacts and topological enhancer-promoter selection

Background CTCF is a key insulator-binding protein, and mammalian genomes contain numerous CTCF sites, many of which are organized in tandem. Results Using CRISPR DNA-fragment editing, in conjunction with chromosome conformation capture, we find that CTCF sites, if located between enhancers and promoters in the protocadherin ( Pcdh ) and β-globin clusters, function as an enhancer-blocking insulator by forming distinct directional chromatin...