Involved in chromosome cohesion during cell cycle and in DNA repair. Central component of cohesin complex. 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 anaphase, the complex is cleaved and dissociates from chromatin, allowing sister chromatids to segregate. Cohesin complexes are composed of the SMC1 and SMC3 heterodimer attached via their SMC hinge domain, MCD1/SCC1 which link them, and IRR1/SCC3, which interacts with MCD1. The cohesin complex also interacts with SCC2, which is required for its association with chromosomes. Associates with chromatin. Before prophase it is scattered along chromosome arms. At anaphase, the MCD1 subunit of the cohesin complex is cleaved, leading to the dissociation of the complex from chromosomes, allowing chromosome separation. The flexible SMC hinge domain, which separates the large intramolecular coiled coil regions, allows the heterotypic interaction with the corresponding domain of SMC1, forming a V-shaped heterodimer. The two heads of the heterodimer are then connected by different ends of the cleavable MCD1 protein, forming a ring structure (By similarity). Acetylation at Lys-112 and Lys-113 by ECO1 is important for genome stability and S phase sister chromatid cohesion. Present with 2660 molecules/cell in log phase SD medium. Belongs to the SMC family. SMC3 subfamily.