Nature Cell Biology 8, 137 - 147 (2005)
Published online: 25 December 2005; | doi:10.1038/ncb1349
GCP-WD is a  -tubulin targeting factor required for centrosomal and chromatin-mediated microtubule nucleationJens Lüders1, Urvashi K. Patel1
& Tim Stearns1, 21
Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. 2
Department of Genetics, Stanford University Medical School, Stanford, CA 94305, USA.
Correspondence should be addressed to Tim Stearns stearns@stanford.edu The  -tubulin ring complex (TuRC) is a large multi-protein complex that is required for microtubule nucleation from the centrosome. Here, we show that the GCP-WD protein (originally named NEDD1) is the orthologue of the Drosophila Dgrip71WD protein, and is a subunit of the human TuRC. GCP-WD has the properties of an attachment factor for the TuRC: depletion or inhibition of GCP-WD results in loss of the TuRC from the centrosome, abolishing centrosomal microtubule nucleation, although the TuRC is intact and able to bind to microtubules. GCP-WD depletion also blocks mitotic chromatin-mediated microtubule nucleation, resulting in failure of spindle assembly. Mitotic phosphorylation of GCP-WD is required for association of -tubulin with the spindle, separately from association with the centrosome. Our results indicate that GCP-WD broadly mediates targeting of the TuRC to sites of microtubule nucleation and to the mitotic spindle, which is essential for spindle formation.
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