cohesion complex

Function

• complex required for cohesion of sister chromatids after DNA replication
• forms a large proteinaceous ring within which sister chromatids can be trapped
• at anaphase, complex is cleaved & dissociates from chromatin, allowing sister chromatids to segregate.
• spindle pole assembly during mitosis
• plays a role in apoptosis
  • RAD21 subunit is cleaved by caspase-3 or caspase-7 early
  • 64 kD RAD21 C-terminal cleavage product translocates to cytoplasm Stucture:
• subunits
  • SMC1L1 or SMC1L2
  • SMC3
  • RAD21
  • STAG1, STAG2 or STAG3 (mutually exclusive)
• cohesin complexes are composed of the SMC1 (SMC1A or SMC1B) & SMC3 heterodimer attached via their hinge domain, RAD21 which link them, & one STAG protein (STAG1, STAG2 or STAG3), which interacts with RAD21

Compartment

• before prophase, it is scattered along chromosome arms
• during prophase, most of cohesin complexes dissociate from chromatin after phosphorylation by PLK, except at centromeres, where cohesin complexes remain
• at anaphase, the RAD21 subunit of the cohesin complex is cleaved, leading to the dissociation of the complex from chromosomes, allowing chromosome separation

More general terms

• molecular complex
• nuclear protein