title: Reconstitution of the augmin complex provides insights into its architecture and function.
abstract: 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.
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Kuo-Chiang
authors.initials: KC
authors.lastname: Hsia
authors.affiliation: Department of Integrated Structure and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Wilson-Kubalek
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Dottore
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Hao
authors.affiliation: Department of Integrated Structure and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Kuang-Lei
authors.initials: KL
authors.lastname: Tsai
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Forth
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shimamoto
authors.affiliation: Department of Integrated Structure and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Milligan
authors.affiliation: Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, New York 10065, USA.
authors.forename: Tarun M
authors.initials: TM
authors.lastname: Kapoor
mesh_terms: D000818:Animals; D002474:Cell-Free System; D004926:Escherichia coli; D006801:Humans; D008677:Metaphase; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000378:metabolism; D008870:Microtubules / Q000737:chemistry / Q000648:ultrastructure; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D008941:Spindle Apparatus / Q000378:metabolism / Q000648:ultrastructure; D014982:Xenopus laevis
chemical_list: C534027:HAUS6 protein, human; C000628759:HAUS8 protein, human; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits