In vivo biochemical analyses reveal distinct roles of β-importins and eEF1A in tRNA subcellular traffic.

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.
Mesh Terms:
Active Transport, Cell Nucleus, Cell Nucleus, Cytoplasm, Eukaryotic Initiation Factors, Karyopherins, Nucleocytoplasmic Transport Proteins, Peptide Elongation Factor 1, Peptide Elongation Factors, Protein Structure, Quaternary, RNA, Transfer, RNA-Binding Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, beta Karyopherins
Genes Dev.
Date: Apr. 01, 2015
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