Aurora-A phosphorylates Augmin complex component Hice1 protein at an N-terminal serine/threonine cluster to modulate its microtubule binding activity during spindle assembly.
J Biol Chem
; 286(34): 30097-106, 2011 Aug 26.
Article
em En
| MEDLINE
| ID: mdl-21705324
ABSTRACT
Proper assembly of mitotic spindles requires Hice1, a spindle-associated protein. Hice1 possesses direct microtubule binding activity at its N-terminal region and contributes to intraspindle microtubule nucleation as a subunit of the Augmin complex. However, whether microtubule binding activity of Hice1 is modulated by mitotic regulators remains unexplored. Here, we found that Aurora-A kinase, a major mitotic kinase, specifically binds to and phosphorylates Hice1. We identified four serine/threonine clusters on Hice1 that can be phosphorylated by Aurora-A in vitro. Of the four clusters, the Ser/Thr-17-21 cluster was the most critical for bipolar spindle assembly, whereas other phospho-deficient point mutants had a minimal effect on spindle assembly. Immunostaining with a phospho-Ser-19/20 phospho-specific antibody revealed that phosphorylated Hice1 primarily localizes to spindle poles during prophase to metaphase but gradually diminishes after anaphase. Consistently, the phospho-mimic 17-21E mutant reduced microtubule binding activity in vitro and diminished localization to spindles in vivo. Furthermore, expression of the 17-21E mutant led to decreased association of Fam29a, an Augmin component, with spindles. On the other hand, expression of the phospho-deficient 17-21A mutant permitted intraspindle nucleation but delayed the separation of early mitotic spindle poles and the timely mitotic progression. Taken together, these results suggest that Aurora-A modulates the microtubule binding activity of Hice1 in a spatiotemporal manner for proper bipolar spindle assembly.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Prófase
/
Proteínas Serina-Treonina Quinases
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Metáfase
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Proteínas Associadas aos Microtúbulos
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Microtúbulos
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Fuso Acromático
Limite:
Humans
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article