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The human decatenation checkpoint

2001; National Academy of Sciences; Volume: 98; Issue: 21 Linguagem: Inglês

10.1073/pnas.221430898

1091-6490

Paula B. Deming, Cheryl A. Cistulli, Hui Zhao, Paul R. Graves, Helen Piwnica‐Worms, Richard S. Paules, C. Stephen Downes, William K. Kaufmann,

Cancer-related Molecular Pathways

Chromatid catenation is actively monitored in human cells, with progression from G 2 to mitosis being inhibited when chromatids are insufficiently decatenated. Mitotic delay was quantified in normal and checkpoint-deficient human cells during treatment with ICRF-193, a topoisomerase II catalytic inhibitor that prevents chromatid decatenation without producing topoisomerase-associated DNA strand breaks. Ataxia telangiectasia (A-T) cells, defective in DNA damage checkpoints, showed normal mitotic delay when treated with ICRF-193. The mitotic delay in response to ICRF-193 was ablated in human fibroblasts expressing an ataxia telangiectasia mutated- and rad3-related (ATR) kinase-inactive ATR allele (ATR ki ). BRCA1-mutant HCC1937 cells also displayed a defect in ICRF-193-induced mitotic delay, which was corrected by expression of wild-type BRCA1. Phosphorylations of hCds1 or Chk1 and inhibition of Cdk1 kinase activity, which are elements of checkpoints associated with DNA damage or replication, did not occur during ICRF-193-induced mitotic delay. Over-expression of cyclin B1 containing a dominant nuclear localization signal, and inhibition of Crm1-mediated nuclear export, reversed ICRF-193-induced mitotic delay. In combination, these results imply that ATR and BRCA1 enforce the decatenation G 2 checkpoint, which may act to exclude cyclin B1/Cdk1 complexes from the nucleus. Moreover, induction of ATR ki produced a 10-fold increase in chromosomal aberrations, further emphasizing the vital role for ATR in genetic stability.