Eukaryotic genomes are organized into higher order chromatin architectures by 
protein-mediated long-range interactions in the nucleus. CCCTC-binding factor 
(CTCF), a sequence-specific transcription factor, serves as a chromatin 
organizer in building this complex chromatin structure by linking chromosomal 
domains. Recent genome-wide studies mapping the binding sites of CTCF and its 
interacting partner, cohesin, using chromatin immunoprecipitation coupled with 
deep sequencing (ChIP-seq) revealded that CTCF globally co-localizes with 
cohesin. This partnership between CTCF and cohesin is emerging as a novel and 
perhaps pivotal aspect of gene regulatory mechanisms, in addition to playing a 
role in the organization of higher order chromatin architecture.