title: Genetic interactions between Brca1 and Gadd45a in centrosome duplication, genetic stability, and neural tube closure.
abstract: GADD45a is a transcription target of the breast tumor suppressor gene BRCA. It was recently shown that mouse embryonic fibroblast cells carrying a targeted deletion of exon 11 of Brca1 (Brca1(Delta11/Delta11)) or a Gadd45A-null mutation (Gadd45a(-/-)) suffer centrosome amplification. To study genetic interactions between these genes during centrosome duplication, we generated Brca1(Delta11/Delta)(11)Gadd45a(-/-) mice by crossing each mutant. We found that all Brca1(Delta11/Delta11)Gadd45a(-/-) embryos at embryonic days 9.5-10.5 were exencephalic and exhibited a high incidence of apoptosis accompanied by altered levels of BAX, BCL-2, and p53. The trigger for these events is likely the genetic instability arising from centrosome amplification that is associated, at least in part, with decreased expression of the NIMA-related kinase NEK2. We demonstrate that small interfering RNA-mediated suppression of Brca1 decreased Nek2 more dramatically in Gadd45a(-/-) cells than in wild-type cells and, conversely, that overexpression of Brca1 and/or Gadd45a up-regulated transcription of Nek2. Furthermore, we show that overexpression of Nek2 in Brca1-specific small interfering RNA-treated wild-type and Gadd45a(-/-) cells repressed abnormal centrosome amplification. These observations suggest that NEK2 plays a role in mediating the actions of BRCA1 and GADD45a in regulating centrosome duplication and in maintaining genetic stability.
authors.affiliation: Genetics of Development and Disease Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wang
authors.forename: Rui-Hong
authors.initials: RH
authors.lastname: Wang
authors.forename: Wenmei
authors.initials: W
authors.lastname: Li
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Xu
authors.forename: M Christine
authors.initials: MC
authors.lastname: Hollander
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Fornace
authors.forename: Chu-Xia
authors.initials: CX
authors.lastname: Deng
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002490:Central Nervous System / Q000033:anatomy & histology* / Q000196:embryology*; D018385:Centrosome / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D042822:Genomic Instability; D005865:Gestational Age; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D000072379:NIMA-Related Kinases; D009436:Neural Tube Defects / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D000097642:GADD45 Proteins
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D000072379:NIMA-Related Kinases; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C499072:Gadd45a protein, mouse; C089441:NEK2 protein, human; C490317:Nek2 protein, mouse