title: Both DNA topoisomerase II-binding protein 1 and BRCA1 regulate the G2-M cell cycle checkpoint.
abstract: Cell cycle checkpoints play a central role in genomic stability. The human DNA topoisomerase II-binding protein 1 (TopBP1) protein contains eight BRCA1 COOH terminus motifs and shares similarities with Cut5, a yeast checkpoint Rad protein. TopBP1 also shares many features with BRCA1. We report that, when expression of TopBP1 protein is inhibited in BRCA1 mutant cells, mimicking a TopBP1, BRCA1 double-negative condition, the G(2)-M checkpoint is strongly abrogated and apoptosis is increased after ionizing radiation. However, a BRCA1-negative or a TopBP1-negative background resulted in only partial abrogation of the G(2)-M checkpoint. The BRCA1 mutant and TopBP1-reduced condition specifically destroys regulation of the Chk1 kinase but not the Chk2 kinase, suggesting involvement in the ataxia telangiectasia-related pathway. These results indicate that both TopBP1 and BRCA1 specifically regulate the G(2)-M checkpoint, partially compensating each function.
authors.affiliation: Department of Radiation Oncology, Case Western Reserve University, Cleveland, Ohio 44106-4942, USA.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamane
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kinsella
mesh_terms: D017209:Apoptosis / Q000502:physiology; D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000502:physiology*; D001943:Breast Neoplasms / Q000473:pathology; D002277:Carcinoma / Q000473:pathology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins; D016195:G2 Phase / Q000235:genetics / Q000502:physiology*; D019398:Genes, BRCA1; D018816:Genes, cdc; D006801:Humans; D008677:Metaphase / Q000235:genetics / Q000502:physiology*; D009363:Neoplasm Proteins / Q000502:physiology; D009687:Nuclear Proteins; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000528:radiation effects; D014410:Tumor Stem Cell Assay; D025521:Tumor Suppressor Proteins
chemical_list: D019313:BRCA1 Protein; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D011993:Recombinant Fusion Proteins; C110513:TOPBP1 protein, human; D025521:Tumor Suppressor Proteins; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases