title: CDC25B overexpression stabilises centrin 2 and promotes the formation of excess centriolar foci.
abstract: CDK-cyclin complexes regulate centriole duplication and microtubule nucleation at specific cell cycle stages, although their exact roles in these processes remain unclear. As the activities of CDK-cyclins are themselves positively regulated by CDC25 phosphatases, we investigated the role of centrosomal CDC25B during interphase. We report that overexpression of CDC25B, as is commonly found in human cancer, results in a significant increase in centrin 2 at the centrosomes of interphase cells. Conversely, CDC25B depletion causes a loss of centrin 2 from the centrosome, which can be rescued by treatment with the proteasome inhibitor MG132. CDC25B overexpression also promotes the formation of excess centrin 2 "foci". These foci can accumulate other centrosome proteins, including γ-tubulin and PCM-1, and can function as microtubule organising centres, indicating that these represent functional centrosomes. Formation of centrin 2 foci can be blocked by specific inhibition of CDK2 but not CDK1. CDK2-mediated phosphorylation of Monopolar spindle 1 (Mps1) at the G1/S transition is essential for the initiation of centrosome duplication, and Mps1 is reported to phosphorylate centrin 2. Overexpression of wild-type or non-degradable Mps1 exacerbated the formation of excess centrin 2 foci induced by CDC25B overexpression, while kinase-dead Mps1 has a protective effect. Together, our data suggest that CDC25B, through activation of a centrosomal pool of CDK2, stabilises the local pool of Mps1 which in turn regulates the level of centrin 2 at the centrosome. Overexpression of CDC25B may therefore contribute to tumourigenesis by perturbing the natural turnover of centrosome proteins such as Mps1 and centrin 2, thus resulting in the de novo assembly of extra-numerary centrosomes and potentiating chromosome instability.
authors.affiliation: Princess Alexandra Hospital, The University of Queensland Diamantina Institute, Brisbane, Queensland, Australia. rboutros@cmri.org.au
authors.forename: Rose
authors.initials: R
authors.lastname: Boutros
authors.forename: Odile
authors.initials: O
authors.lastname: Mondesert
authors.forename: Corinne
authors.initials: C
authors.lastname: Lorenzo
authors.forename: Puji
authors.initials: P
authors.lastname: Astuti
authors.forename: Grant
authors.initials: G
authors.lastname: McArthur
authors.forename: Megan
authors.initials: M
authors.lastname: Chircop
authors.forename: Bernard
authors.initials: B
authors.lastname: Ducommun
authors.forename: Brian
authors.initials: B
authors.lastname: Gabrielli
mesh_terms: D016203:CDC2 Protein Kinase / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D018385:Centrosome / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D059748:Proteolysis; D015854:Up-Regulation; D020687:cdc25 Phosphatases / Q000235:genetics / Q000378:metabolism*
chemical_list: C472752:CETN2 protein, human; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D051357:Cyclin-Dependent Kinase 2; C075840:TTK protein, human; C517008:CDC25B protein, human; D020687:cdc25 Phosphatases; D046988:Proteasome Endopeptidase Complex