Nuclear export receptor Xpo1/Crm1 is physically and functionally linked to the spindle pole body in budding yeast

Mol Cell Biol. 2008 Sep;28(17):5348-58. doi: 10.1128/MCB.02043-07. Epub 2008 Jun 23.

Abstract

The spindle pole body (SPB) represents the microtubule organizing center in the budding yeast Saccharomyces cerevisiae. It is a highly structured organelle embedded in the nuclear membrane, which is required to anchor microtubules on both sides of the nuclear envelope. The protein Spc72, a component of the SPB, is located at the cytoplasmic face of this organelle and serves as a receptor for the gamma-tubulin complex. In this paper we show that it is also a binding partner of the nuclear export receptor Xpo1/Crm1. Xpo1 binds its cargoes in a Ran-dependent fashion via a short leucine-rich nuclear export signal (NES). We show that binding of Spc72 to Xpo1 depends on Ran-GTP and a functional NES in Spc72. Mutations in this NES have severe consequences for mitotic spindle morphology in vivo. This is also the case for xpo1 mutants, which show a reduction in cytoplasmic microtubules. In addition, we find a subpopulation of Xpo1 localized at the SPB. Based on these data, we propose a functional link between Xpo1 and the SPB and discuss a role for this exportin in spindle biogenesis in budding yeast.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Cell Nucleus / metabolism*
  • Exportin 1 Protein
  • Guanosine Triphosphate / metabolism
  • Karyopherins / metabolism*
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism
  • Microtubules / metabolism
  • Monomeric GTP-Binding Proteins / metabolism
  • Mutation / genetics
  • Nuclear Export Signals
  • Nuclear Proteins / metabolism
  • Peptide Fragments / metabolism
  • Protein Binding
  • Protein Transport
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism
  • Spindle Apparatus / metabolism*

Substances

  • GSP1 protein, S cerevisiae
  • Karyopherins
  • Microtubule-Associated Proteins
  • Nuclear Export Signals
  • Nuclear Proteins
  • Peptide Fragments
  • Receptors, Cytoplasmic and Nuclear
  • SPC72 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Guanosine Triphosphate
  • Monomeric GTP-Binding Proteins