title: ATR enforces the topoisomerase II-dependent G2 checkpoint through inhibition of Plk1 kinase.
abstract: An ATR-dependent G(2) checkpoint responds to inhibition of topoisomerase II and delays entry into mitosis by sustaining nuclear exclusion of cyclin B1-Cdk1 complexes. Here we report that induction of this checkpoint with ICRF-193, a topoisomerase II catalytic inhibitor that does not cause DNA damage, was associated with an ATR-dependent inhibition of polo-like kinase 1 (Plk1) kinase activity and a decrease in cyclin B1 phosphorylation. Expression of constitutively active Plk1 but not wild type Plk1 reversed ICRF-193-induced mitotic delay in HeLa cells, suggesting that Plk1 kinase activity is important for the checkpoint response to ICRF-193. G(2)/M synchronized normal human fibroblasts, when treated with ICRF-193, showed a decrease in cyclin B1 phosphorylation and Plk1 kinase activity despite high cyclin B1-Cdk1 kinase activity. G(2) fibroblasts that were treated with caffeine to override the checkpoint response to ICRF-193 displayed a high incidence of chromosomal aberrations. Taken together, these results suggest that ATR-dependent inhibition of Plk1 kinase activity may be one mechanism to regulate cyclin B1 phosphorylation and sustain nuclear exclusion during the G(2) checkpoint response to topoisomerase II inhibition. Moreover, the results demonstrate an important role for the topoisomerase II-dependent G(2) checkpoint in the preservation of human genomic stability.
authors.affiliation: Department of Pathology and Laboratory Medicine, Lineberger Comprehensive Cancer Center, and Center for Environmental Health and Susceptibility, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Paula B
authors.initials: PB
authors.lastname: Deming
authors.forename: Kristina G
authors.initials: KG
authors.lastname: Flores
authors.forename: C Stephen
authors.initials: CS
authors.lastname: Downes
authors.forename: Richard S
authors.initials: RS
authors.lastname: Paules
authors.forename: William K
authors.initials: WK
authors.lastname: Kaufmann
mesh_terms: D000483:Alleles; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D002869:Chromosome Aberrations; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D016195:G2 Phase; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D008954:Models, Biological; D010766:Phosphorylation; D011233:Precipitin Tests; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D013997:Time Factors; D014162:Transfection; D000097869:Polo-Like Kinase 1
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D016203:CDC2 Protein Kinase; D002110:Caffeine; D018797:Cell Cycle Proteins; D000697:Central Nervous System Stimulants; D019926:Cyclin B; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases; D004250:DNA Topoisomerases, Type II; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1; C534699:CCNB1 protein, human; C576597:ATR protein, human