Abstract
Cohesin and CTCF are key to the 3D folding of interphase chromosomes. Cohesin forms chromatin loops via loop extrusion, a process that involves the formation and enlargement of DNA loops. The architectural protein CTCF controls this process by acting as an anchor for chromatin looping. How CTCF controls cohesin has long been a mystery. Recent work shows that CTCF dictates chromatin looping via a direct interaction of its N-terminus with cohesin. CTCF's ability to regulate chromatin looping turns out to also be partially dependent on several RNA-binding domains. In this review, we discuss recent insights and consider how cohesin and CTCF together may orchestrate the folding of the genome into chromosomal loops.