A requirement for breast-cancer-associated gene 1 (BRCA1) in the spindle checkpoint.
BRCA1-associated breast cancer exhibits significantly higher levels of chromosomal abnormalities than sporadic breast cancers. However, the molecular mechanisms regarding the roles of BRCA1 in maintaining genome integrity remain elusive. By using a mouse model deficient for Brca1 full-length isoform (Brca1(Delta11/Delta11)), we found that Brca1(Delta11/Delta11) cells displayed decreased expression of a number of genes that are involved in the spindle checkpoint, including Mad2, which is a key component of spindle checkpoint that inhibits anaphase-promoting complex. We showed that Brca1(Delta11/Delta11) cells failed to arrest at metaphase in the presence of nocodazole and underwent apoptosis because of activation of p53. Consistently, reconstitution of Mad2 in Brca1(Delta11/Delta11) cells partially restored the spindle checkpoint and attenuated apoptosis. By using UBR60 cells, which carry tetracycline-regulated expression of BRCA1, we demonstrated that BRCA1 binds to transcription factor OCT-1 and up-regulates the transcription of MAD2. Furthermore, we showed that the induction of BRCA1 to endogenous MAD2 or transfected MAD2 luciferase reporter in UBR60 cells was completely inhibited by acute suppression of BRCA1 by RNA interference. These data reveal a role of BRCA1 in maintaining genome integrity by interplaying with p53 and genes that are involved in the spindle checkpoint and apoptosis.
Wang
Rui-Hong
RH
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Yu
Hongtao
H
Deng
Chu-Xia
CX
D000818:Animals; D017209:Apoptosis; D019313:BRCA1 Protein / Q000172:deficiency / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins; D002460:Cell Line; D048750:Cell Nucleus Division / Q000235:genetics; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D064246:Mad2 Proteins; D008677:Metaphase / Q000235:genetics; D051379:Mice; D015739:Nocodazole / Q000494:pharmacology; D050811:Octamer Transcription Factor-1; D012097:Repressor Proteins; D017384:Sequence Deletion; D008941:Spindle Apparatus; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D019313:BRCA1 Protein; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; C494166:Pou2f1 protein, mouse; D012097:Repressor Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D015739:Nocodazole