title: A nuclear export sequence located on a beta-strand in fibroblast growth factor-1.
abstract: Receptor-bound and endocytosed fibroblast growth factor-1 (FGF-1) is able to cross the vesicle membrane and translocate to cytosol and nucleus. This suggests an intracellular role of FGF-1, which also signals by activating transmembrane FGF receptors. Phosphorylation of internalized FGF-1 by nuclear protein kinase C delta induces rapid export from the nuclei by a leptomycin B-sensitive pathway. In the present work, we have searched for and identified a Leu-rich nuclear export sequence (NES) at the C terminus of FGF-1 required for its nuclear export and able to confer nuclear export activity to a reporter protein in an in vivo system. Mutants where hydrophobic amino acids within the NES were exchanged for alanine exhibited reduced or abolished nuclear export. As demonstrated in co-immunoprecipitation experiments, a complex containing FGF-1, exportin-1, and its co-factor Ran-GTP, was formed in vitro. Formation of this complex in vivo was demonstrated by a peroxisomal targeting assay. Formation of the FGF-1-exportin-1-Ran-GTP complex in vitro as well as nuclear export of FGF-1 in vivo was dependent on phosphorylation of FGF-1, and it was abolished by leptomycin B. The FGF-1 NES was found to be situated along a beta-strand, which has not been reported before, since NESs usually are alpha-helical.
authors.affiliation: Centre for Cancer Biomedicine, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Centre, Montebello, University of Oslo, 0310 Oslo, Norway.
authors.forename: Trine
authors.initials: T
authors.lastname: Nilsen
authors.forename: Ken R
authors.initials: KR
authors.lastname: Rosendal
authors.forename: Vigdis
authors.initials: V
authors.lastname: Sørensen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Wesche
authors.forename: Sjur
authors.initials: S
authors.lastname: Olsnes
authors.forename: Antoni
authors.initials: A
authors.lastname: Wiedłocha
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D019943:Amino Acid Substitution; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002474:Cell-Free System / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D016220:Fibroblast Growth Factor 1 / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D046912:Multiprotein Complexes; D020125:Mutation, Missense; D041681:NIH 3T3 Cells; D049790:Nuclear Export Signals; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D000903:Antibiotics, Antineoplastic; D005231:Fatty Acids, Unsaturated; D016220:Fibroblast Growth Factor 1; D028884:Karyopherins; D046912:Multiprotein Complexes; D049790:Nuclear Export Signals; D051745:Protein Kinase C-delta; D018160:Receptors, Cytoplasmic and Nuclear; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C038753:leptomycin B