Figure EV5. Loop formation depends on cohesin and is regulated by CTCF, WAPL, and PDS5 proteins.

• A
  Graphical illustration of how cohesin might mediate loop extrusion. Cohesin binds to chromatin, extrudes a chromatin loop and stalls upon encountering CTCF bound at convergently oriented CTCF sites.
• B
  In the absence of cohesin, chromatin loops are eliminated.
• C
  n the absence of CTCF, cohesin extrudes chromatin loops but fails to stall at convergently oriented CTCF binding sites.
• D, E
  In the absence of WAPL (D) or PDS5A/B (E), cohesin extrudes longer chromatin loops, which occur more frequently between regions of non‐convergent (D) or single CTCF sites (E). While in the absence of Wapl loop extrusion still halts at occupied CTCF sites, in the absence of PDS5A/B loop extrusion may halt less readily, resulting in fewer specific loops called.