title: Cloning and characterization of human karyopherin beta3.
abstract: Nuclear import of classical nuclear localization sequence-bearing proteins is mediated by karyopherin alpha/beta1 heterodimers. A second nuclear import pathway, mediated by karyopherin beta2 (transportin), recently was described for mRNA-binding proteins. Here we report the cloning and characterization of human karyopherin beta3, which may be involved in a third pathway for nuclear import. Karyopherin beta3 was localized mainly to the cytosol and the nucleus, particularly the nuclear rim. It bound to several of the repeat-containing nucleoporins (Nup358, Nup214, Nup153, Nup98, and p62) in overlay and solution-binding assays and was competed away by karyopherin beta1. For Nup98, we localized this binding to the peptide repeat-containing region. Karyopherin beta3 contains two putative Ran-binding homology regions and bound to Ran-GTP in a solution-binding assay with much higher affinity than to Ran-GDP. Furthermore, it interacted with two ribosomal proteins in an overlay assay. We suggest that karyopherin beta3 is a nuclear transport factor that may mediate the import of some ribosomal proteins into the nucleus.
authors.affiliation: Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Yaseen
authors.forename: G
authors.initials: G
authors.lastname: Blobel
mesh_terms: D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000737:chemistry; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005455:Fluorescent Antibody Technique; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C107940:IPO5 protein, human; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D011506:Proteins; D011994:Recombinant Proteins; D012269:Ribosomal Proteins; D028961:beta Karyopherins; C093350:nuclear pore complex protein 98; C043816:ribosomal protein L23, E coli; D006160:Guanosine Triphosphate; D020931:ran GTP-Binding Protein