Cleavable component of the cohesin complex, involved in chromosome cohesion during cell cycle. The cohesin complex is required for the cohesion of sister chromatids after DNA replication. The cohesin complex apparently forms a large proteinaceous ring within which sister chromatids can be trapped. At metaphase-anaphase transition, this protein is cleaved by cut1 and dissociates from chromatin, allowing sister chromatids to segregate. Also involved in the DNA double-strand-break (DSB) repair system. Cohesin complexes are composed of the psm1/smc1 and psm3/smc3 heterodimer attached via their hinge domain, rad21/scc1 which link them, and psc3/scc3, which interacts with rad21. Interacts with ssl3. Associates with chromatin. Cohesin complex mainly associates with broad centromere region. Also associates with mating-type heterochromatic region. Hyperphosphorylated during S and G2 phases. Proteolytic cleavage of a fraction of hyperphosphorylated form at the onset of anaphase may be essential for the proper progression of anaphase and sister chromatid separation. Belongs to the rad21 family.