beta-subunit of nuclear pore-targeting complex (importin-beta) can be exported from the nucleus in a Ran-independent manner

J Biol Chem. 1999 Feb 12;274(7):3946-52. doi: 10.1074/jbc.274.7.3946.

Abstract

The nuclear export of importin-alpha is mediated by CAS, which is related to importin-beta, whereas the mechanism for the export of importin-beta remains unclear. In this study, we demonstrate that the nuclear export of importin-beta is mediated by the nuclear pore complex-binding domain of this molecule. Insensitivity to leptomycin B indicates that its export is not mediated by a leucine-rich nuclear export signal-specific receptor, CRM1. Furthermore, the nuclear export of importin-beta was not inhibited by co-injection with a GTPase-deficient Ran mutant (G19V). The cell line tsBN2 contains a temperature-sensitive point mutation in the RCC1 gene, which encodes a guanine nucleotide exchange factor of Ran. At the nonpermissive temperature, importin-beta was exported from the nucleus of these cells, even when RanGAP1, a GTPase-activating protein for Ran, was co-injected. These results not only provide support for the view that Ran-dependent GTP hydrolysis is not required for the nuclear export of importin-beta but also indicate that nuclear RanGTP is not essential for its export. As a result, we propose that importin-beta can be recycled from the nucleus alone in a Ran-independent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Fusion
  • Cell Line
  • Cell Nucleus / metabolism*
  • Cricetinae
  • Fatty Acids, Unsaturated / metabolism
  • GTP Phosphohydrolases / metabolism
  • GTP-Binding Proteins / metabolism
  • Hydrolysis
  • Karyopherins
  • Mice
  • Nuclear Proteins / metabolism*
  • Protein Conformation
  • Respirovirus
  • alpha Karyopherins
  • beta Karyopherins
  • ran GTP-Binding Protein

Substances

  • Fatty Acids, Unsaturated
  • Karyopherins
  • Kpna2 protein, mouse
  • Kpnb1 protein, mouse
  • Nuclear Proteins
  • alpha Karyopherins
  • beta Karyopherins
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • ran GTP-Binding Protein
  • leptomycin B