title: A Rae1-containing ribonucleoprotein complex is required for mitotic spindle assembly.
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.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Blower
authors.forename: Maxence
authors.initials: M
authors.lastname: Nachury
authors.forename: Rebecca
authors.initials: R
authors.lastname: Heald
authors.forename: Karsten
authors.initials: K
authors.lastname: Weis
mesh_terms: D000818:Animals; D002457:Cell Extracts; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008870:Microtubules / Q000378:metabolism; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D028961:beta Karyopherins / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D002457:Cell Extracts; D034521:Nuclear Matrix-Associated Proteins; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; C500752:RAE1 protein, Xenopus; C490522:RAE1 protein, human; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D029867:Xenopus Proteins; D028961:beta Karyopherins; C093350:nuclear pore complex protein 98; D020931:ran GTP-Binding Protein