title: Cyclin A and B functions in the early Drosophila embryo.
abstract: In eukaryotes, mitotic cyclins localize differently in the cell and regulate different aspects of the cell cycle. We investigated the relationship between subcellular localization of cyclins A and B and their functions in syncytial preblastoderm Drosophila embryos. During early embryonic cycles, cyclin A was always concentrated in the nucleus and present at a low level in the cytoplasm. Cyclin B was predominantly cytoplasmic, and localized within nuclei only during late prophase. Also, cyclin B colocalized with metaphase but not anaphase spindle microtubules. We changed maternal gene doses of cyclins A and B to test their functions in preblastoderm embryos. We observed that increasing doses of cyclin B increased cyclin B-Cdk1 activity, which correlated with shorter microtubules and slower microtubule-dependent nuclear movements. This provides in vivo evidence that cyclin B-Cdk1 regulates microtubule dynamics. In addition, the overall duration of the early nuclear cycles was affected by cyclin A but not cyclin B levels. Taken together, our observations support the hypothesis that cyclin B regulates cytoskeletal changes while cyclin A regulates the nuclear cycles. Varying the relative levels of cyclins A and B uncoupled the cytoskeletal and nuclear events, so we speculate that a balance of cyclins is necessary for proper coordination during these embryonic cycles.
authors.affiliation: Department of Zoology, Box 351800, University of Washington, Seattle, WA 98195-1800, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Stiffler
authors.forename: J Y
authors.initials: JY
authors.lastname: Ji
authors.forename: S
authors.initials: S
authors.lastname: Trautmann
authors.forename: C
authors.initials: C
authors.lastname: Trusty
authors.forename: G
authors.initials: G
authors.lastname: Schubiger
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D019925:Cyclin A / Q000378:metabolism*; D019926:Cyclin B / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D005260:Female; D018878:Limb Buds / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008938:Mitosis
chemical_list: C503698:CycB protein, Drosophila; D019925:Cyclin A; D019926:Cyclin B; D029721:Drosophila Proteins; D016203:CDC2 Protein Kinase