CDK5RAP2 stimulates microtubule nucleation by the γ-tubulin ring complex

• Main Authors: Choi, Yuk Kwan, Liu, Pengfei, Sze, Siu Kwan, Dai, Chao, Qi, Robert Z.
• Other Authors: School of Biological Sciences
• Format: Article
• Language: English
• Published: 2011
• Subjects: DRNTU::Science::Biological sciences::Molecular biology
• Online Access: https://hdl.handle.net/10356/101395; http://hdl.handle.net/10220/6796
• Institution: Nanyang Technological University

CDK5RAP2 is a human microcephaly protein that contains a γ-tubulin complex (γ-TuC)–binding domain conserved in Drosophila melanogaster centrosomin and Schizosaccharomyces pombe Mto1p and Pcp1p, which are γ-TuC–tethering proteins. In this study, we show that this domain within CDK5RAP2 associates with the γ-tubulin ring complex (γ-TuRC) to stimulate its microtubule-nucleating activity and is therefore referred to as the γ-TuRC–mediated nucleation activator (γ-TuNA). γ-TuNA but not its γ-TuC–binding-deficient mutant stimulates microtubule nucleation by purified γ-TuRC in vitro and induces extensive, γ-TuRC-dependent nucleation of microtubules in a microtubule regrowth assay. γ-TuRC bound to γ-TuNA contains NME7, FAM128A/B, and actin in addition to γ-tubulin and GCP2–6. RNA interference–mediated depletion of CDK5RAP2 impairs both centrosomal and acentrosomal microtubule nucleation, although γ-TuRC assembly is unaffected. Collectively, these results suggest that the γ-TuNA found in CDK5RAP2 has regulatory functions in γ-TuRC–mediated microtubule nucleation.