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Structural analysis of the role of TPX2 in branching microtubule nucleation

Author(s): Alfaro-Aco, Raymundo; Thawani, Akanksha; Petry, Sabine

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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.
Publication Date: Apr-2017
Electronic Publication Date: 6-Mar-2017
Citation: Alfaro-Aco, Raymundo, Thawani, Akanksha, Petry, Sabine. (2017). Structural analysis of the role of TPX2 in branching microtubule nucleation.. The Journal of cell biology, 216 (4), 983 - 997. doi:10.1083/jcb.201607060
DOI: doi:10.1083/jcb.201607060
ISSN: 0021-9525
EISSN: 1540-8140
Pages: 983 - 997
Language: eng
Type of Material: Journal Article
Journal/Proceeding Title: The Journal of Cell Biology
Version: Final published version. This is an open access article.

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