English: A. Cohesin is comprised of four core structural subunits: RAD21, SMC1, SMC3, and a SA protein (SA1 or SA2). PDS5, WAPL, and Sororin are cohesin-associate proteins. Sororin has not been found in yeast. B. One-ring model. C. Handcuff model. Figure adapted with modifications from Zhang and Pati. *This Wiki-Gene report on RAD21 is based on a review article “Cohesin Subunit RAD21: from Biology to Disease” by Cheng et al published in Gene