Fig. 3
From: Getting the genome in shape: the formation of loops, domains and compartments
Different scenarios for cohesin-mediated chromatin looping. Three hypotheses for the strategy by which the cohesin complex is involved in the formation of chromatin loops. a After initial association of cohesin to one roadblock (such as CTCF), cohesin holds on to this site, and the flanking chromatin is pulled through until a second roadblock is encountered. b The cohesin ring remains open when the complex is attached to one roadblock. Only when a second cognate anchor sequence comes in close proximity does the ring close efficiently. c Cohesin embraces the DNA anchors of a loop that are already held together by other proteins (left-hand cartoons); its embrace stabilizes maintenance of the loops (right-hand cartoons)