CM1-driven assembly and activation of Yeast γ-Tubulin Small Complex underlies microtubule nucleation

Brilot, A. F.; Lyon, A.; Zelter, A.; Viswanath, S.; Maxwell, A.; MacCoss, M. J.; Muller, E. G.; Sali, A.; Davis, T. N.; Agard, D. A.

doi:10.1101/2020.11.21.392803

bioRxiv · 10.1101/2020.11.21.392803

CM1-driven assembly and activation of Yeast γ-Tubulin Small Complex underlies microtubule nucleation

Brilot, A. F.·Lyon, A.·Zelter, A.·Viswanath, S.·Maxwell, A.·MacCoss, M. J.·Muller, E. G.·Sali, A.·Davis, T. N.·Agard, D. A.

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Abstract

Microtubule (MT) nucleation is regulated by the {gamma}-tubulin ring complex ({gamma}TuRC), conserved from yeast to humans. In Saccharomyces cerevisiae, {gamma}TuRC is composed of seven identical {gamma}-tubulin small complex ({gamma}TuSC) sub-assemblies which associate helically to template microtubule growth. {gamma}TuRC assembly provides a key point of regulation for the MT cytoskeleton. Here we combine cross-linking mass spectrometry (XL-MS), X-ray crystallography and cryo-EM structures of both monomeric and dimeric {gamma}TuSCs, and open and closed helical {gamma}TuRC assemblies in complex with Spc110p to elucidate the mechanisms of {gamma}TuRC assembly. {gamma}TuRC assembly is substantially aided by the evolutionarily conserved CM1 motif in Spc110p spanning a pair of adjacent {gamma}TuSCs. By providing the highest resolution and most complete views of any {gamma}TuSC assembly, our structures allow phosphorylation sites to be mapped, surprisingly suggesting that they are mostly inhibitory. A comparison of our structures with the CM1 binding site in the human {gamma}TuRC structure at the interface between GCP2 and GCP6 allows for the interpretation of significant structural changes arising from CM1 helix binding to metazoan {gamma}TuRC.

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Brilot, A. F., Lyon, A., Zelter, A., Viswanath, S., Maxwell, A., MacCoss, M. J., Muller, E. G., Sali, A., Davis, T. N., Agard, D. A.. 2020-11-22. CM1-driven assembly and activation of Yeast γ-Tubulin Small Complex underlies microtubule nucleation. https://doi.org/10.1101/2020.11.21.392803

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