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Nat Cell Biol September 1, 2014; 16 (9): 852-63.
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Reconstitution of the augmin complex provides insights into its architecture and function.

Hsia KC , Wilson-Kubalek EM , Dottore A , Hao Q , Tsai KL , Forth S , Shimamoto Y , Milligan RA , Kapoor TM .

Proper microtubule nucleation during cell division requires augmin, a microtubule-associated hetero-octameric protein complex. In current models, augmin recruits γ-tubulin, through the carboxyl terminus of its hDgt6 subunit to nucleate microtubules within spindles. However, augmin''s biochemical complexity has restricted analysis of its structural organization and function. Here, we reconstitute human augmin and show that it is a Y-shaped complex that can adopt multiple conformations. Further, we find that a dimeric sub-complex retains in vitro microtubule-binding properties of octameric complexes, but not proper metaphase spindle localization. Addition of octameric augmin complexes to Xenopus egg extracts promotes microtubule aster formation, an activity enhanced by Ran-GTP. This activity requires microtubule binding, but not the characterized hDgt6 γ-tubulin-recruitment domain. Tetrameric sub-complexes induce asters, but activity and microtubule bundling within asters are reduced compared with octameric complexes. Together, our findings shed light on augmin''s structural organization and microtubule-binding properties, and define subunits required for its function in organizing microtubule-based structures.

PubMed ID: 25173975
PMC ID: PMC4244909
Article link: Nat Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: ran

References [+] :
Bettencourt-Dias, Centrosome biogenesis and function: centrosomics brings new understanding. 2007, Pubmed