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

Cell. 2005 Apr 22;121(2):223-34. doi: 10.1016/j.cell.2005.02.016.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Extracts
  • Female
  • HeLa Cells
  • Humans
  • Male
  • Microtubules / metabolism
  • Nuclear Matrix-Associated Proteins / genetics
  • Nuclear Matrix-Associated Proteins / metabolism*
  • Nuclear Pore Complex Proteins / metabolism
  • Nucleocytoplasmic Transport Proteins / genetics
  • Nucleocytoplasmic Transport Proteins / metabolism*
  • Oocytes / metabolism
  • RNA, Messenger / metabolism
  • Ribonucleoproteins / metabolism*
  • Spermatozoa / metabolism
  • Spindle Apparatus / metabolism*
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism*
  • Xenopus laevis
  • beta Karyopherins / metabolism
  • ran GTP-Binding Protein / metabolism


  • Cell Extracts
  • Nuclear Matrix-Associated Proteins
  • Nuclear Pore Complex Proteins
  • Nucleocytoplasmic Transport Proteins
  • RAE1 protein, Xenopus
  • RAE1 protein, human
  • RNA, Messenger
  • Ribonucleoproteins
  • Xenopus Proteins
  • beta Karyopherins
  • nuclear pore complex protein 98
  • ran GTP-Binding Protein