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bioRxiv · 10.1101/2025.11.20.689565

Phosphorylation remodels the mitotic centrosome matrix to generate bipartite gamma-tubulin complex docking sites

Ohta, M.·Arakawa, O.·Gu, Y.·Tian, W.·Corbett, K. D.·Desai, A.·Oegema, K.
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Abstract

Mitotic centrosomes consist of centrioles surrounded by a proteinaceous matrix that docks and activates {gamma}-tubulin complexes ({gamma}TuCs) to nucleate microtubules for spindle assembly. During mitotic entry, phosphorylation at centrosomes remodels CDK5RAP2 family matrix proteins to generate {gamma}TuC docking sites. We address the mechanism of this conversion using C. elegans SPD-5 as a model. We show that SPD-5 contains two regions, PRGB1 and PRGB2, that are each sufficient for Polo-Like Kinase 1 (PLK1) phosphorylation-regulated {gamma}TuC binding. We define key phosphosites in each region and uncover autoinhibition mediated by interactions within and between them. PRGB2 is dimeric and requires {gamma}TuCs containing the Mozart family microprotein MZT-1 for binding, whereas PRGB1 is monomeric and binds independently of MZT-1. Our results support PLK1 phosphorylation inducing a conformational change that enables MZT-1-dependent PRGB2 binding, which in turn relieves PRGB1 inhibition. Such a multi-step mechanism would ensure robust spindle assembly by restricting microtubule nucleation in space and time.

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Ohta, M., Arakawa, O., Gu, Y., Tian, W., Corbett, K. D., Desai, A., Oegema, K.. 2025-11-21. Phosphorylation remodels the mitotic centrosome matrix to generate bipartite gamma-tubulin complex docking sites. https://doi.org/10.1101/2025.11.20.689565

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