CM1-driven assembly and activation of Yeast γ-Tubulin Small Complex underlies microtubule nucleation
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Microtubule (MT) nucleation is regulated by the γ-tubulin ring complex (γTuRC), conserved from yeast to humans. In Saccharomyces cerevisiae, γTuRC is composed of seven identical γ-tubulin small complex (γTuSC) sub-assemblies which associate helically to template microtubule growth. γTuRC 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 monomeric and dimeric γTuSC and open and closed helical γTuRC assemblies in complex with Spc110p to elucidate the mechanisms of γTuRC assembly. γTuRC assembly is substantially aided by the evolutionarily conserved CM1 motif in Spc110p spanning a pair of adjacent γTuSCs. By providing the highest resolution and most complete views of any γTuSC assembly, our structures allow phosphorylation sites to be mapped, suggesting their role in regulating spindle pole body attachment and ring assembly. We further identify a structurally analogous CM1 binding site in the human γTuRC structure at the interface between GCP2 and GCP6, which allows for the interpretation of significant structural changes arising from CM1 helix binding in metazoan γTuRC structures.
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This page provides public access to data associated with Brilot et al. (2020).