title: BRCA2 interacts with the cytoskeletal linker protein plectin to form a complex controlling centrosome localization.
abstract: The breast cancer susceptibility gene (BRCA2) is localized mainly in the nucleus where it plays an important role in DNA damage repair. Some BRCA2 protein is also present in the centrosome. Here, we demonstrate that BRCA2 interacts with plectin, a cytoskeletal cross-linker protein, and that this interaction controls the position of the centrosome. Phosphorylation of plectin by cyclin-dependent kinase 1/cyclin B (CDK1/CycB) kinase has been reported to abolish its cross-linking function during mitosis. Here, we induced phosphorylation of plectin in prepared fractions of HeLa cells by adding activated CDK1/CycB kinase. Consequently, there was significant dissociation of the centrosome from the nuclear membrane. Plectin has six homologous ankyrin-like repeat domains (termed PLEC M1-M6). Using a pull-down assay, we found that GST-PLEC M1 and a GST-C-terminal region fusion protein (which comprised PLEC M6, along with an adjacent vimentin site) interacted with BRCA2. Since each PLEC module exhibits high homology to the others, the possibility of all six domains participating in this interaction was indicated. Moreover, when PLEC M1 was overexpressed in HeLa cells, it competed with endogenous plectin and inhibited the BRCA2-plectin interaction. This inhibitory effect resulted in dissociation of the centrosomes from the nucleus and increased the rate of micronuclei formation which may lead to carcinogenesis. In addition, when either BRCA2 or plectin was suppressed by the appropriate siRNA, a similar change in centrosomal positioning was observed. We suggest that the BRCA2-plectin interaction plays an important role in the regulation of centrosome localization and also that displacement of the centrosome may result in genomic instability and cancer development.
authors.affiliation: Department of Endocrine Surgery and Gastrointestinal Surgery, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Niwa
authors.forename: Hiroko
authors.initials: H
authors.lastname: Saito
authors.forename: Shinobu
authors.initials: S
authors.lastname: Imajoh-ohmi
authors.forename: Michio
authors.initials: M
authors.lastname: Kaminishi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Seto
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Miki
authors.forename: Akira
authors.initials: A
authors.lastname: Nakanishi
mesh_terms: D051017:Apoptosis Regulatory Proteins; D024682:BRCA2 Protein / Q000502:physiology*; D016203:CDC2 Protein Kinase / Q000502:physiology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000473:pathology; D018385:Centrosome / Q000502:physiology*; D019926:Cyclin B / Q000502:physiology; D056744:Cyclin B1; D006801:Humans; D047468:Immunoprecipitation; D009369:Neoplasms / Q000209:etiology; D051190:Plectin / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary
chemical_list: D051017:Apoptosis Regulatory Proteins; C118024:BLID protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D051190:Plectin; D016203:CDC2 Protein Kinase