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Cell. 2005 Apr 22;121(2):223-34.

A Rae1-containing ribonucleoprotein complex is required for mitotic spindle assembly.

Author information

1
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA.

Abstract

Centrosome-independent microtubule polymerization around chromosomes has been shown to require a local gradient of RanGTP, which discharges mitotic cargoes from the nuclear import receptor importin beta. Here, we have used an activity-based assay in Xenopus egg extracts to purify the mRNA export protein Rae1 as a spindle assembly factor regulated by this pathway. Rae1 is a microtubule-associated protein that binds directly to importin beta. Depletion of Rae1 from extracts or cells severely inhibits mitotic spindle assembly. A purified Rae1 complex stabilizes microtubules in egg extracts in a RanGTP/importin beta-regulated manner. Interestingly, Rae1 exists in a large ribonucleoprotein complex, which requires RNA for its activity to control microtubule dynamics in vitro. Furthermore, we provide evidence that RNA associates with the mitotic spindle and that it plays a direct, translation-independent role in spindle assembly. Our studies reveal an unexpected function for RNA in spindle morphogenesis.

PMID:
15851029
DOI:
10.1016/j.cell.2005.02.016
[Indexed for MEDLINE]
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