Drosophila Wee1 interacts with members of the gammaTURC and is required for proper mitotic-spindle morphogenesis and positioning.
BACKGROUND
Wee1 kinases delay entry into mitosis by phosphorylating and inactivating cyclin-dependent kinase 1 (Cdk1). Loss of this activity in many systems, including Drosophila, leads to premature mitotic entry.


RESULTS
We report here that Drosophila Wee1 (dwee1) mutant embryos show mitotic-spindle defects that include ectopic foci of microtubule organization, formation of multipolar spindles from adjacent centrosome pairs, and promiscuous interactions between neighboring spindles. Furthermore, centrosomes are displaced from the embryo cortex in dwee1 mutants. These defects are not observed to the same extent in embryos in which nuclei also enter mitosis prematurely as a result of a lack of checkpoint control or in embryos with elevated Cdk1 activity. dWee1 physically interacts with members of the gamma-tubulin ring complex (gammaTuRC), and gamma-tubulin is phosphorylated in a dwee1-dependent manner in embryo extracts.


CONCLUSIONS
Some of the abnormalities in dwee1 mutant embryos cannot be explained by premature entry into mitosis or bulk elevation of Cdk1 activity. Instead, dWee1 is also required for phosphorylation of gamma-tubulin, centrosome positioning, and mitotic-spindle integrity. We propose a model to account for these requirements.
Stumpff
Jason
J
Department of Molecular, Cellular, and Developmental Biology, 347 UCB, University of Colorado, Boulder Boulder, Colorado 80309, USA.
Kellogg
Douglas R
DR
Krohne
Kathleen A
KA
Su
Tin Tin
TT
D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D018385:Centrosome / Q000378:metabolism / Q000502:physiology; D002846:Chromatography, Affinity; D004330:Drosophila / Q000378:metabolism / Q000502:physiology*; D015180:Electrophoresis, Gel, Two-Dimensional; D005455:Fluorescent Antibody Technique; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D009024:Morphogenesis; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism / Q000502:physiology*; D019076:Transgenes / Q000235:genetics; D014404:Tubulin / Q000378:metabolism*
D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D014404:Tubulin; D011505:Protein-Tyrosine Kinases; C508847:Wee1 protein, Drosophila