title: Cep63 recruits Cdk1 to the centrosome: implications for regulation of mitotic entry, centrosome amplification, and genome maintenance.
abstract: Centrosomes are central regulators of mitosis that are often amplified in cancer cells. Centrosomes function both as organizers of the mitotic spindle and as reaction centers to trigger activation of Cdk1 and G(2)/M transition in the cell cycle, but their functional organization remains incomplete. Recent proteomic studies have identified novel components of the human centrosome including Cep63, a protein of unknown function that Xenopus studies have implicated in mitotic spindle assembly and spindle inactivation after DNA damage. Here, we report that human Cep63 binds to and recruits Cdk1 to centrosomes, and thereby regulates mitotic entry. RNAi-mediated Cep63 depletion in U2OS cancer cells induced polyploidization through mitotic skipping. Elicitation of this phenotype was associated with downregulation of centrosomal Cdk1, mimicking the phenotype induced by direct depletion of Cdk1. In contrast, Cep63 overexpression induced de novo centrosome amplification during cell-cycle interphase. Induction of this phenotype was suppressible by cell treatment with the Cdk inhibitor roscovitine. In a survey of 244 neuroblastoma cases, Cep63 mRNA overexpression was associated with MYCN oncogene amplification and poor prognosis. In cultured cells, Cep63 overexpression was associated with an enhancement in replication-induced DNA breakage. Together, our findings define human Cep63 as a centrosomal recruitment factor for Cdk1 that is essential for mitotic entry, providing a physical link between the centrosome and the cell-cycle machinery.
authors.affiliation: Clinical Cooperation Unit Molecular Hematology/Oncology, German Cancer Research Center and Department of Medicine V, University of Heidelberg, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Löffler
authors.forename: Anne
authors.initials: A
authors.lastname: Fechter
authors.forename: Marc
authors.initials: M
authors.lastname: Matuszewska
authors.forename: Rainer
authors.initials: R
authors.lastname: Saffrich
authors.forename: Martin
authors.initials: M
authors.lastname: Mistrik
authors.forename: Joachim
authors.initials: J
authors.lastname: Marhold
authors.forename: Christin
authors.initials: C
authors.lastname: Hornung
authors.forename: Frank
authors.initials: F
authors.lastname: Westermann
authors.forename: Jiri
authors.initials: J
authors.lastname: Bartek
authors.forename: Alwin
authors.initials: A
authors.lastname: Krämer
mesh_terms: D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D018385:Centrosome / Q000187:drug effects / Q000378:metabolism*; D015536:Down-Regulation; D015894:Genome, Human / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007399:Interphase / Q000235:genetics; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000235:genetics; D000071447:N-Myc Proto-Oncogene Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011123:Polyploidy; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077546:Roscovitine
chemical_list: C508298:CEP63 protein, human; D018797:Cell Cycle Proteins; C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D047428:Protein Kinase Inhibitors; D011687:Purines; D000077546:Roscovitine; D049452:Green Fluorescent Proteins; D016203:CDC2 Protein Kinase