title: Caspase proteolysis of the cohesin component RAD21 promotes apoptosis.
abstract: Caspases are a conserved family of proteases that play a critical role in the execution of apoptosis by cleaving key cellular proteins at Asp residues and modifying their function. Using an expression cloning strategy we recently developed, we isolated human RAD21/SCC1/MCD1 as a novel caspase substrate. RAD21 is a component of the cohesin complex that holds sister chromatids together during mitosis and repairs double-strand DNA breaks. Interestingly, RAD21 is cleaved by a caspase-like Esp1/separase at the onset of anaphase to trigger sister chromatid separation. Here, we demonstrate that human RAD21 is preferentially cleaved at Asp(279) by caspases-3 and -7 in vitro to generate two major proteolytic products of approximately 65 and 48 kDa. Moreover, we show that RAD21 is specifically proteolyzed by caspases into a similarly sized 65-kDa carboxyl-terminal product in cells undergoing apoptosis in response to diverse stimuli. We also demonstrate that caspase proteolysis of RAD21 precedes apoptotic chromatin condensation and has important functional consequences, viz. the partial removal of RAD21 from chromatin and the production of a proapoptotic carboxyl-terminal cleavage product that amplifies the cell death signal. Taken together, these findings point to an entirely novel function of RAD21 in the execution of apoptosis.
authors.affiliation: Robert H. Lurie Comprehensive Cancer Center and the Department of Medicine, Northwestern University Medical School, Chicago, IL 60611, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Merideth
authors.initials: M
authors.lastname: Kamradt
authors.forename: Mary
authors.initials: M
authors.lastname: Mulcahy
authors.forename: Young
authors.initials: Y
authors.lastname: Byun
authors.forename: Huiling
authors.initials: H
authors.lastname: Xu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McKay
authors.forename: Vincent L
authors.initials: VL
authors.lastname: Cryns
mesh_terms: D017209:Apoptosis; D001224:Aspartic Acid / Q000737:chemistry; D001665:Binding Sites; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D016923:Cell Death; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008164:Luminescent Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D000097722:Cohesins
chemical_list: D001224:Aspartic Acid; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D000097722:Cohesins; C429022:RAD21 protein, human; C505407:CASP3 protein, human; C505520:CASP7 protein, human