title: Reengineering ribosome export.
abstract: Large cargoes require multiple receptors for efficient transport through the nuclear pore complex. The 60S ribosomal subunit is one of the bulkiest transport cargoes, and in yeast three different receptors, Crm1, Mex67/Mtr2, and Arx1, collaborate in its export. However, only Crm1, recruited by the adapter Nmd3, appears to be conserved for 60S export in higher eukaryotes. We asked if export of the large subunit requires specific receptors. We made protein fusions between mutant Nmd3 and various export receptors. Surprisingly, fusions of Mex67, the tRNA exportin Los1, Mtr2, Cse1, or Msn5 to Nmd3, lacking its Crm1-dependent nuclear export signal (NES), all functioned in export. Furthermore, these chimeric proteins supported 60S export even in the presence of the Crm1 inhibitor leptomycin B, indicating that export was now independent of Crm1. These results suggest that there is not a requirement for a specific export receptor for the large subunit, as recruitment of any receptor will suffice. Finally we show that the addition of an NES directly to the 60S ribosomal subunit protein Rpl3 promotes export. These results imply remarkable flexibility in the export pathway for the 60S subunit and help explain how different export receptors could have evolved in different eukaryotic lineages.
authors.affiliation: Institute for Cellular and Molecular Biology, the University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Kai-Yin
authors.initials: KY
authors.lastname: Lo
authors.forename: Arlen W
authors.initials: AW
authors.lastname: Johnson
mesh_terms: D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D028884:Karyopherins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D008958:Models, Molecular; D049790:Nuclear Export Signals; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000097606:Exportin 1 Protein
chemical_list: D005231:Fatty Acids, Unsaturated; D019204:GTP-Binding Proteins; D028884:Karyopherins; D049790:Nuclear Export Signals; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C106898:MEX67 protein, S cerevisiae; C117894:NMD3 protein, S cerevisiae; C475026:LSG1 protein, S cerevisiae; C038753:leptomycin B