Structural analysis of the role of TPX2 in branching microtubule nucleation.

TitleStructural analysis of the role of TPX2 in branching microtubule nucleation.
Publication TypeJournal Article
Year of Publication2017
AuthorsAlfaro-Aco, R, Thawani, A, Petry, S
JournalJ Cell Biol
Date Published2017 Apr 03
KeywordsAnimals, Cell Cycle Proteins, Microtubule-Associated Proteins, Microtubule-Organizing Center, Microtubules, Nuclear Proteins, Protein Binding, Spindle Apparatus, Tubulin, Xenopus laevis

<p>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 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.</p>

Alternate JournalJ Cell Biol
PubMed ID28264915
PubMed Central IDPMC5379942
Grant ListDP2 GM123493 / GM / NIGMS NIH HHS / United States
R00 GM100013 / GM / NIGMS NIH HHS / United States
T32 GM007388 / GM / NIGMS NIH HHS / United States
/ HHMI / Howard Hughes Medical Institute / United States