title: In vivo biochemical analyses reveal distinct roles of β-importins and eEF1A in tRNA subcellular traffic.
abstract: Bidirectional tRNA movement between the nucleus and the cytoplasm serves multiple biological functions. To gain a biochemical understanding of the mechanisms for tRNA subcellular dynamics, we developed in vivo β-importin complex coimmunoprecipitation (co-IP) assays using budding yeast. Our studies provide the first in vivo biochemical evidence that two β-importin family members, Los1 (exportin-t) and Msn5 (exportin-5), serve overlapping but distinct roles in tRNA nuclear export. Los1 assembles complexes with RanGTP and tRNA. Both intron-containing pre-tRNAs and spliced tRNAs, regardless of whether they are aminoacylated, assemble into Los1-RanGTP complexes, documenting that Los1 participates in both primary nuclear export and re-export of tRNAs to the cytoplasm. In contrast, β-importin Msn5 preferentially assembles with RanGTP and spliced, aminoacylated tRNAs, documenting its role in tRNA nuclear re-export. Tef1/2 (the yeast form of translation elongation factor 1α [eEF1A]) aids the specificity of Msn5 for aminoacylated tRNAs to form a quaternary complex consisting of Msn5, RanGTP, aminoacylated tRNA, and Tef1/2. Assembly and/or stability of this quaternary complex requires Tef1/2, thereby facilitating efficient re-export of aminoacylated tRNAs to the cytoplasm.
authors.affiliation: Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Hsiao-Yun
authors.initials: HY
authors.lastname: Huang
authors.affiliation: Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA hopper.64@osu.edu.
authors.forename: Anita K
authors.initials: AK
authors.lastname: Hopper
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm; D039642:Eukaryotic Initiation Factors / Q000378:metabolism; D028884:Karyopherins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D020648:Peptide Elongation Factor 1 / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D012343:RNA, Transfer / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: D039642:Eukaryotic Initiation Factors; D028884:Karyopherins; C401306:MSN5 protein, S cerevisiae; C110033:MTR10 protein, S cerevisiae; D029543:Nucleocytoplasmic Transport Proteins; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C410826:TEF1 protein, S cerevisiae; C057183:TEF2 protein, S cerevisiae; D028961:beta Karyopherins; D012343:RNA, Transfer
keywords: Los1; Msn5; Mtr10; Saccharomyces cerevisiae; Tef1/2; nuclear export
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