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XB-ART-1991
Cell April 22, 2005; 121 (2): 223-34.
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A Rae1-containing ribonucleoprotein complex is required for mitotic spindle assembly.

Blower MD , Nachury M , Heald R , Weis K .


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.

PubMed ID: 15851029
Article link: Cell
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: kpnb1 rae1

References :
Funabiki, Two birds with one stone--dealing with nuclear transport and spindle assembly. 2005, Pubmed