Drosophila melanogaster gamma-TuRC is dispensable for targeting gamma-tubulin to the centrosome and microtubule nucleation.
In metazoans, gamma-tubulin acts within two main complexes, gamma-tubulin small complexes (gamma-TuSCs) and gamma-tubulin ring complexes (gamma-TuRCs). In higher eukaryotes, it is assumed that microtubule nucleation at the centrosome depends on gamma-TuRCs, but the role of gamma-TuRC components remains undefined. For the first time, we analyzed the function of all four gamma-TuRC-specific subunits in Drosophila melanogaster: Dgrip75, Dgrip128, Dgrip163, and Dgp71WD. Grip-motif proteins, but not Dgp71WD, appear to be required for gamma-TuRC assembly. Individual depletion of gamma-TuRC components, in cultured cells and in vivo, induces mitotic delay and abnormal spindles. Surprisingly, gamma-TuSCs are recruited to the centrosomes. These defects are less severe than those resulting from the inhibition of gamma-TuSC components and do not appear critical for viability. Simultaneous cosilencing of all gamma-TuRC proteins leads to stronger phenotypes and partial recruitment of gamma-TuSC. In conclusion, gamma-TuRCs are required for assembly of fully functional spindles, but we suggest that gamma-TuSC could be targeted to the centrosomes, which is where basic microtubule assembly activities are maintained.
Centre de Recherche en Pharmacologie, Santé, UMR 2587, Centre National de la Recherche Scientifique-Pierre Fabre, Institut de Sciences et Technologies du Médicament de Toulouse, 31432 Toulouse, Cedex 4, France.
Christel
C
Vérollet
Nathalie
N
Colombié
Thomas
T
Daubon
Henri-Marc
HM
Bourbon
Michel
M
Wright
Brigitte
B
Raynaud-Messina
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D016764:Cell Polarity; D002478:Cells, Cultured; D018385:Centrosome / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D004331:Drosophila melanogaster; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation; D014404:Tubulin / Q000378:metabolism*
D029721:Drosophila Proteins; C419558:Grip128 protein, Drosophila; C419559:Grip163 protein, Drosophila; C480600:Grip71 protein, Drosophila; C469730:Grip75 protein, Drosophila; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D014404:Tubulin