CCCTC-binding factor (CTCF) is a master organizer of genome spatial organization 
and plays an important role in mediating extensive chromatin interactions. 
Circular chromosome conformation capture (4C) is a high-throughput approach that 
allows genome-wide screening for unknown potential interaction partners. Using a 
conserved CTCF binding site on the Bcl11b locus as bait, an interaction partner 
at the Arhgap6 locus on a different chromosome was identified by 4C. Additional 
experiments verified that the interchromatin interaction between the Bcl11b and 
Arhgap6 loci was cell-type specific, which was cooperatively mediated by CTCF 
and cohesin. Functional analysis showed that the interchromatin interaction 
partners were repressing regulatory elements. These results indicate that 
interaction chromatin loops regulate the expression of the relevant genes.