title: Genetic interactions between Cdk1-CyclinB and the Separase complex in Drosophila.
abstract: Cdk1-CycB plays a key role in regulating many aspects of cell-cycle events, such as cytoskeletal dynamics and chromosome behavior during mitosis. To investigate how Cdk1-CycB controls the coordination of these events, we performed a dosage-sensitive genetic screen, which is based on the observations that increased maternal CycB (four extra gene copies) leads to higher Cdk1-CycB activity in early Drosophila embryos, delays anaphase onset, and generates a sensitized non-lethal phenotype at the blastoderm stage (defined as six cycB phenotype). Here, we report that mutations in the gene three rows (thr) enhance, while mutations in pimples (pim, encoding Drosophila Securin) or separase (Sse) suppress, the sensitized phenotype. In Drosophila, both Pim and Thr are known to regulate Sse activity, and activated Sse cleaves a Cohesin subunit to initiate anaphase. Compared with the six cycB embryos, reducing Thr in embryos with more CycB further delays the initiation of anaphase, whereas reducing either Pim or Sse has the opposite effect. Furthermore, nuclei move slower during cortical migration in embryos with higher Cdk1-CycB activity, whereas reducing either Pim or Sse suppresses this phenotype by causing a novel nuclear migration pattern. Therefore, our genetic screen has identified all three components of the complex that regulates sister chromatid separation, and our observations indicate that interactions between Cdk1-CycB and the Pim-Thr-Sse complex are dosage sensitive.
authors.affiliation: Department of Biology, University of Washington, Seattle, WA 98195-1800, USA. jji@partners.org
authors.forename: Jun-Yuan
authors.initials: JY
authors.lastname: Ji
authors.forename: Justin
authors.initials: J
authors.lastname: Crest
authors.forename: Gerold
authors.initials: G
authors.lastname: Schubiger
mesh_terms: D000705:Anaphase / Q000502:physiology*; D000818:Animals; D016203:CDC2 Protein Kinase / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002842:Chromatids / Q000235:genetics / Q000502:physiology*; D002868:Chromosomal Proteins, Non-Histone; D002874:Chromosome Mapping; D019926:Cyclin B / Q000235:genetics*; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics; D064247:Separase; D000097722:Cohesins
chemical_list: D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D019926:Cyclin B; D029721:Drosophila Proteins; D010450:Endopeptidases; D005656:Fungal Proteins; D009687:Nuclear Proteins; D012330:RNA, Double-Stranded; D064247:Separase; D000097722:Cohesins; C503698:CycB protein, Drosophila; C413708:PIM protein, Drosophila; C085015:thr protein, Drosophila; C577989:Sse protein, Drosophila