Essential component of cohesin complex; a complex 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. The cohesin complex may also play a role in spindle pole assembly during mitosis. Required for centromere cohesion maintenance at anaphase I and for the monopolar orientation of the kinetochores during both male and female meiosis. Also involved in mitosis. {ECO:0000269|PubMed:16176934; ECO:0000269|PubMed:19533160}.