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.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Cell Compartmentation
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Cell Nucleus / chemistry
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Cloning, Molecular
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Cytoplasm / chemistry
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DNA, Complementary / genetics
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DNA-Binding Proteins / genetics*
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DNA-Binding Proteins / isolation & purification
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DNA-Binding Proteins / metabolism
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Escherichia coli / genetics
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Escherichia coli Proteins*
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Fluorescent Antibody Technique
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Guanosine Triphosphate / metabolism
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HeLa Cells
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Humans
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Membrane Proteins / genetics*
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Membrane Proteins / isolation & purification
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Membrane Proteins / metabolism
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Molecular Sequence Data
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Nuclear Pore Complex Proteins*
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Nuclear Proteins / genetics*
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Nuclear Proteins / isolation & purification
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Nuclear Proteins / metabolism
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Protein Binding
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Proteins*
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Recombinant Proteins / metabolism
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Ribosomal Proteins / metabolism
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Sequence Homology, Amino Acid
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beta Karyopherins
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ran GTP-Binding Protein
Substances
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DNA, Complementary
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DNA-Binding Proteins
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Escherichia coli Proteins
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IPO5 protein, human
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Membrane Proteins
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Nuclear Pore Complex Proteins
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Nuclear Proteins
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Proteins
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Recombinant Proteins
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Ribosomal Proteins
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beta Karyopherins
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nuclear pore complex protein 98
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ribosomal protein L23, E coli
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Guanosine Triphosphate
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ran GTP-Binding Protein