title: Utp9p facilitates Msn5p-mediated nuclear reexport of retrograded tRNAs in Saccharomyces cerevisiae.
abstract: Utp9p is a nucleolar protein that is part of a subcomplex containing several U3 snoRNA-associated proteins including Utp8p, which is a protein that shuttles aminoacyl-tRNAs from the nucleolus to the nuclear tRNA export receptors Los1p and Msn5p in Saccharomyces cerevisiae. Here we show that Utp9p is also an intranuclear component of the Msn5p-mediated nuclear tRNA export pathway. Depletion of Utp9p caused nuclear accumulation of mature tRNAs derived from intron-containing precursors, but not tRNAs made from intronless pre-tRNAs. Utp9p binds tRNA directly and saturably, and copurifies with Utp8p, Gsp1p, and Msn5p, but not with Los1p or aminoacyl-tRNA synthetases. Utp9p interacts directly with Utp8p, Gsp1p, and Msn5p in vitro. Furthermore, Gsp1p forms a complex with Msn5p and Utp9p in a tRNA-dependent manner. However, Utp9p does not shuttle between the nucleus and the cytoplasm. Because tRNA splicing occurs in the cytoplasm and the spliced tRNAs are retrograded back to the nucleus, we propose that Utp9p facilitates nuclear reexport of retrograded tRNAs. Moreover, the data suggest that Utp9p together with Utp8p translocate aminoacyl-tRNAs from the nucleolus to Msn5p and assist with formation of the Msn5p-tRNA-Gsp1p-GTP export complex.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
authors.forename: Manoja B K
authors.initials: MB
authors.lastname: Eswara
authors.forename: Andrew T
authors.initials: AT
authors.lastname: McGuire
authors.forename: Jacqueline B
authors.initials: JB
authors.lastname: Pierce
authors.forename: Dev
authors.initials: D
authors.lastname: Mangroo
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C080324:GSP1 protein, S cerevisiae; D028884:Karyopherins; C408090:Los1 protein, S cerevisiae; C401306:MSN5 protein, S cerevisiae; D046912:Multiprotein Complexes; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C524393:Utp8 protein, S cerevisiae; C547588:Utp9 protein, S cerevisiae; D012343:RNA, Transfer; D020559:Monomeric GTP-Binding Proteins; D000604:Amino Acyl-tRNA Synthetases