Role of Sister Chromatid Cohesion in the Apoptotic Response of Normal and Malignant Mammary Cells with Known Aneuploidy

摘要

The purpose of the study was to identify the effector molecules that act as a link between cell proliferation, cell survival and chromosomes stability. We have hypothesized that chromosomal segregation and apoptotic pathways are linked and have a role in the development of aneuploidy in breast tumors. Rad21 is one of the major cohesin subunits that holds sister chromatids together until anaphase, when proteolytic cleavage by separase, allows chromosomal separation. We show that cleavage of human Rad21 (hRad21) also occurs during apoptosis. Induction of apoptosis in multiple human cell lines results in the early generation of 64 kDa and 60 kDa carboxy terminal hRad21 cleavage products. We biochemically mapped a apoptotic cleavage site at residue Asp (D)279 of hRad21. This apoptotic cleavage site is distinct from mitotic cleavage sites previously described. hRad21 is a nuclear protein, however, the cleaved 64 kDa carboxy-terminal product is translocated to the cytoplasm early in apoptosis before chromatin condensation and nuclear fragmentation. Overexpression of the 64 kDa cleavage product results in apoptosis in MCF-7 breast cancer cells. Given the role of hRad21 in chromosome cohesion, the cleaved C-terminal product and its translocation to the cytoplasm may act as a nuclear signal for apoptosis. Deregulation of Rad21 cleavage may play a role in breast cancer pathogenesis.