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Proc Natl Acad Sci U S A. Feb 28, 1995; 92(5): 1769–1773.
PMCID: PMC42601

Identification of a protein complex that is required for nuclear protein import and mediates docking of import substrate to distinct nucleoporins.

Abstract

We have identified and characterized a 9S protein complex from a Xenopus ovary cytosolic subfraction (fraction A) that constitutes this fraction's activity in recognizing a model nuclear import substrate and docking it at the nuclear pore complex. Because of its function, the complex is termed karyopherin. The 54- and 56-kDa subunits of the complex are termed alpha 1 and alpha 2, respectively, and the 97-kDa subunit is termed beta. In an alternative approach we have identified karyopherin beta from a rat liver cytosolic subfraction A by using immobilized rat nucleoporin Nup98 in a single, affinity-based enrichment step. We have molecularly cloned and sequenced rat karyopherin beta. Comparison with protein sequence data banks showed no significant similarity to other known proteins. Using nitrocellulose-immobilized rat liver nuclear envelope proteins and nuclear import substrate as a ligand, we found Xenopus fraction A-dependent binding to at least three bona fide nucleoporins (Nup214, Nup153, and Nup98) and to a candidate nucleoporin with an estimated molecular mass of 270 kDa. We propose that these nucleoporins function as docking proteins for karyopherin-mediated binding of substrate in a nuclear import/export pathway across the nuclear pore complex.

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Selected References

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  • Forbes DJ. Structure and function of the nuclear pore complex. Annu Rev Cell Biol. 1992;8:495–527. [PubMed]
  • Dingwall C, Laskey RA. Nuclear targeting sequences--a consensus? Trends Biochem Sci. 1991 Dec;16(12):478–481. [PubMed]
  • Adam SA, Marr RS, Gerace L. Nuclear protein import in permeabilized mammalian cells requires soluble cytoplasmic factors. J Cell Biol. 1990 Sep;111(3):807–816. [PMC free article] [PubMed]
  • Adam SA, Gerace L. Cytosolic proteins that specifically bind nuclear location signals are receptors for nuclear import. Cell. 1991 Sep 6;66(5):837–847. [PubMed]
  • Adam EJ, Adam SA. Identification of cytosolic factors required for nuclear location sequence-mediated binding to the nuclear envelope. J Cell Biol. 1994 May;125(3):547–555. [PMC free article] [PubMed]
  • Moore MS, Blobel G. The two steps of nuclear import, targeting to the nuclear envelope and translocation through the nuclear pore, require different cytosolic factors. Cell. 1992 Jun 12;69(6):939–950. [PubMed]
  • Moore MS, Blobel G. The GTP-binding protein Ran/TC4 is required for protein import into the nucleus. Nature. 1993 Oct 14;365(6447):661–663. [PubMed]
  • Moore MS, Blobel G. Purification of a Ran-interacting protein that is required for protein import into the nucleus. Proc Natl Acad Sci U S A. 1994 Oct 11;91(21):10212–10216. [PMC free article] [PubMed]
  • Coutavas E, Ren M, Oppenheim JD, D'Eustachio P, Rush MG. Characterization of proteins that interact with the cell-cycle regulatory protein Ran/TC4. Nature. 1993 Dec 9;366(6455):585–587. [PubMed]
  • Blobel G, Potter VR. Nuclei from rat liver: isolation method that combines purity with high yield. Science. 1966 Dec 30;154(3757):1662–1665. [PubMed]
  • Fernandez J, DeMott M, Atherton D, Mische SM. Internal protein sequence analysis: enzymatic digestion for less than 10 micrograms of protein bound to polyvinylidene difluoride or nitrocellulose membranes. Anal Biochem. 1992 Mar;201(2):255–264. [PubMed]
  • Richardson WD, Mills AD, Dilworth SM, Laskey RA, Dingwall C. Nuclear protein migration involves two steps: rapid binding at the nuclear envelope followed by slower translocation through nuclear pores. Cell. 1988 Mar 11;52(5):655–664. [PubMed]
  • Feldherr CM, Kallenbach E, Schultz N. Movement of a karyophilic protein through the nuclear pores of oocytes. J Cell Biol. 1984 Dec;99(6):2216–2222. [PMC free article] [PubMed]
  • Davis LI, Blobel G. Identification and characterization of a nuclear pore complex protein. Cell. 1986 Jun 6;45(5):699–709. [PubMed]
  • Moore MS, Blobel G. A G protein involved in nucleocytoplasmic transport: the role of Ran. Trends Biochem Sci. 1994 May;19(5):211–216. [PubMed]
  • Radu A, Blobel G, Wozniak RW. Nup155 is a novel nuclear pore complex protein that contains neither repetitive sequence motifs nor reacts with WGA. J Cell Biol. 1993 Apr;121(1):1–9. [PMC free article] [PubMed]
  • Kraemer D, Wozniak RW, Blobel G, Radu A. The human CAN protein, a putative oncogene product associated with myeloid leukemogenesis, is a nuclear pore complex protein that faces the cytoplasm. Proc Natl Acad Sci U S A. 1994 Feb 15;91(4):1519–1523. [PMC free article] [PubMed]
  • Sukegawa J, Blobel G. A nuclear pore complex protein that contains zinc finger motifs, binds DNA, and faces the nucleoplasm. Cell. 1993 Jan 15;72(1):29–38. [PubMed]
  • Melchior F, Paschal B, Evans J, Gerace L. Inhibition of nuclear protein import by nonhydrolyzable analogues of GTP and identification of the small GTPase Ran/TC4 as an essential transport factor. J Cell Biol. 1993 Dec;123(6 Pt 2):1649–1659. [PMC free article] [PubMed]
  • Rout MP, Wente SR. Pores for thought: nuclear pore complex proteins. Trends Cell Biol. 1994 Oct;4(10):357–365. [PubMed]
  • Panté N, Bastos R, McMorrow I, Burke B, Aebi U. Interactions and three-dimensional localization of a group of nuclear pore complex proteins. J Cell Biol. 1994 Aug;126(3):603–617. [PMC free article] [PubMed]
  • Cordes VC, Reidenbach S, Köhler A, Stuurman N, van Driel R, Franke WW. Intranuclear filaments containing a nuclear pore complex protein. J Cell Biol. 1993 Dec;123(6 Pt 1):1333–1344. [PMC free article] [PubMed]

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