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XB-ART-53171
J Cell Biol January 1, 2017; 216 (4): 983-997.
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Structural analysis of the role of TPX2 in branching microtubule nucleation.

Alfaro-Aco R , Thawani A , Petry S .


Abstract
The mitotic spindle consists of microtubules (MTs), which are nucleated by the γ-tubulin ring complex (γ-TuRC). How the γ-TuRC gets activated at the right time and location remains elusive. Recently, it was uncovered that MTs nucleate from preexisting MTs within the mitotic spindle, which requires the protein TPX2, but the mechanism basis for TPX2 action is unknown. Here, we investigate the role of TPX2 in branching MT nucleation. We establish the domain organization of Xenopus laevis TPX2 and define the minimal TPX2 version that stimulates branching MT nucleation, which we find is unrelated to TPX2''s ability to nucleate MTs in vitro. Several domains of TPX2 contribute to its MT-binding and bundling activities. However, the property necessary for TPX2 to induce branching MT nucleation is contained within newly identified γ-TuRC nucleation activator motifs. Separation-of-function mutations leave the binding of TPX2 to γ-TuRC intact, whereas branching MT nucleation is abolished, suggesting that TPX2 may activate γ-TuRC to promote branching MT nucleation.

PubMed ID: 28264915
PMC ID: PMC5379942
Article link: J Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: kif11 mapre1 pde4dip tpx2 tubgcp5


Article Images: [+] show captions
References [+] :
Albee, Xenopus TACC3/maskin is not required for microtubule stability but is required for anchoring microtubules at the centrosome. 2008, Pubmed, Xenbase