In vitro reconstitution of centrosome assembly and function: the central role of gamma-tubulin.
The centrosome nucleates microtubule polymerization, affecting microtubule number, polarity, and structure. We use an in vitro system based on extracts of Xenopus eggs to examine the role of gamma-tubulin in centrosome assembly and function. gamma-Tubulin is present in the cytoplasm of frog eggs and vertebrate somatic cells in a large approximately 25S complex. The egg extracts assemble centrosomes around sperm centrioles. Formation of a centrosome in the extract requires both the gamma-tubulin complex and ATP and can take place in the absence of microtubules. gamma-Tubulin is not present on the sperm prior to incubation in extract, but is recruited from the cytoplasm during centrosome assembly. The gamma-tubulin complex also binds to microtubules, likely the minus end, independent of the centrosome. These results suggest that gamma-tubulin is an essential component of the link between the centrosome and the microtubule, probably playing a direct role in microtubule nucleation.
Stearns
T
T
Department of Biochemistry and Biophysics, University of California Medical School, San Francisco 94143.
Kirschner
M
M
D000818:Animals; D003593:Cytoplasm / Q000648:ultrastructure; D003599:Cytoskeleton / Q000648:ultrastructure*; D008297:Male; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000276:immunology / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D009865:Oocytes / Q000648:ultrastructure; D012995:Solubility; D013094:Spermatozoa / Q000648:ultrastructure; D008941:Spindle Apparatus / Q000648:ultrastructure; D013768:Tetrahymena / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism*; D014982:Xenopus laevis
D008869:Microtubule-Associated Proteins; D014404:Tubulin