title: Nmd3p is a Crm1p-dependent adapter protein for nuclear export of the large ribosomal subunit.
abstract: In eukaryotic cells, nuclear export of nascent ribosomal subunits through the nuclear pore complex depends on the small GTPase Ran. However, neither the nuclear export signals (NESs) for the ribosomal subunits nor the receptor proteins, which recognize the NESs and mediate export of the subunits, have been identified. We showed previously that Nmd3p is an essential protein from yeast that is required for a late step in biogenesis of the large (60S) ribosomal subunit. Here, we show that Nmd3p shuttles and that deletion of the NES from Nmd3p leads to nuclear accumulation of the mutant protein, inhibition of the 60S subunit biogenesis, and inhibition of the nuclear export of 60S subunits. Moreover, the 60S subunits that accumulate in the nucleus can be coimmunoprecipitated with the NES-deficient Nmd3p. 60S subunit biogenesis and export of truncated Nmd3p were restored by the addition of an exogenous NES. To identify the export receptor for Nmd3p we show that Nmd3p shuttling and 60S export is blocked by the Crm1p-specific inhibitor leptomycin B. These results identify Crm1p as the receptor for Nmd3p export. Thus, export of the 60S subunit is mediated by the adapter protein Nmd3p in a Crm1p-dependent pathway.
authors.affiliation: Section of Molecular Genetics and Microbiology and the Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Ho
authors.forename: G
authors.initials: G
authors.lastname: Kallstrom
authors.forename: A W
authors.initials: AW
authors.lastname: Johnson
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D005656:Fungal Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005799:Genes, Dominant / Q000502:physiology; D028884:Karyopherins; D009154:Mutation / Q000502:physiology; D011233:Precipitin Tests; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D028884:Karyopherins; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C117894:NMD3 protein, S cerevisiae