Format

Send to

Choose Destination
Curr Biol. 2014 Apr 14;24(8):896-903. doi: 10.1016/j.cub.2014.03.006. Epub 2014 Apr 3.

Activation of the γ-tubulin complex by the Mto1/2 complex.

Author information

1
Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Swann Building, Mayfield Road, Edinburgh EH9 3JR, UK.
2
Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Swann Building, Mayfield Road, Edinburgh EH9 3JR, UK. Electronic address: ken.sawin@ed.ac.uk.

Abstract

The multisubunit γ-tubulin complex (γ-TuC) is critical for microtubule nucleation in eukaryotic cells, but it remains unclear how the γ-TuC becomes active specifically at microtubule-organizing centers (MTOCs) and not more broadly throughout the cytoplasm. In the fission yeast Schizosaccharomyces pombe, the proteins Mto1 and Mto2 form the Mto1/2 complex, which interacts with the γ-TuC and recruits it to several different types of cytoplasmic MTOC sites. Here, we show that the Mto1/2 complex activates γ-TuC-dependent microtubule nucleation independently of localizing the γ-TuC. This was achieved through the construction of a "minimal" version of Mto1/2, Mto1/2[bonsai], that does not localize to any MTOC sites. By direct imaging of individual Mto1/2[bonsai] complexes nucleating single microtubules in vivo, we further determine the number and stoichiometry of Mto1, Mto2, and γ-TuC subunits Alp4 (GCP2) and Alp6 (GCP3) within active nucleation complexes. These results are consistent with active nucleation complexes containing ∼13 copies each of Mto1 and Mto2 per active complex and likely equimolar amounts of γ-tubulin. Additional experiments suggest that Mto1/2 multimers act to multimerize the fission yeast γ-tubulin small complex and that multimerization of Mto2 in particular may underlie assembly of active microtubule nucleation complexes.

PMID:
24704079
PMCID:
PMC3989768
DOI:
10.1016/j.cub.2014.03.006
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center