double-strand-break repair protein rad21 homolog (hHR2, nuclear matrix protein 1, NXP-1, SCC1 homolog, RAD21, HR21, KIAA0078, NXP1)

Function

• cleaved component of cohesion complex
• at metaphase-anaphase transition, RAD21 is cleaved by ESPL1, dissociating cohesion complex from chromatin, allowing sister chromatids to segregate.
• 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 & may act as a nuclear signal to initiate cytoplasmic events involved in apoptosis
• becomes hyperphosphorylated in M phase of cell cycle
• dissociation of cohesin from chromosome arms during prophase may be partly due to RAD21 phosphorylation by PLK

Structure

T

• C-terminal part associates with the head of SMC1A
• the N-terminal part binds to the head of SMC3
• belongs to the rad21 family

Compartment

• nucleus
• associates with chromatin
• before prophase it is scattered along chromosome arms
• during prophase, most of cohesin complexes dissociate from chromatin probably because of phosphorylation by PLK, except at centromeres, where cohesin complexes remain
• at anaphase, RAD21 is cleaved by separase/ESPL1, leading to the dissociation of the complex from chromosomes, allowing chromosome separation
• once cleaved by caspase-3, the C-terminal 64 kD cleavage product translocates to the cytoplasm, where it may trigger apoptosis

Polymorphism

• some radiosensitive cancer patients seem to have Arg-481 instead of the conserved Gly-481
• it may be that this mutation could contribute to radiosensitivity

More general terms

• protein subunit
• phosphoprotein

Component of

• cohesion complex

Database

• OMIM: https://mirror.omim.org/entry/606462
• UniProt: http://www.uniprot.org/uniprot/O60216.html