Cex1p is a novel cytoplasmic component of the Saccharomyces cerevisiae nuclear tRNA export machinery.
The Saccharomyces cerevisiae Yor112wp, which we named Cex1p, was identified using a yeast tRNA three-hybrid interaction approach and an in vivo nuclear tRNA export assay as a cytoplasmic component of the nuclear tRNA export machinery. Cex1p binds tRNA saturably, and associates with the nuclear pore complex by interacting directly with Nup116p. Cex1p co-purifies with the nuclear tRNA export receptors Los1p and Msn5p, the eukaryotic elongation factor eEF-1A, which delivers aminoacylated tRNAs to the ribosome, and the RanGTPase Gsp1p, but not with Cca1p, a tRNA maturation enzyme that facilitates translocation of non-aminoacylated tRNAs across the nuclear pore complex. Depletion of Cex1p and eEF-1A or Los1p significantly reduced the efficiency of nuclear tRNA export. Cex1p interacts with Los1p but not with eEF-1A in vitro. These findings suggest that Cex1p is a component of the nuclear aminoacylation-dependent tRNA export pathway in S. cerevisiae. They also suggest that Cex1p collects aminoacyl-tRNAs from the nuclear export receptors at the cytoplasmic side of the nuclear pore complex, and transfers them to eEF-1A using a channelling mechanism.
McGuire
Andrew T
AT
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Mangroo
Dev
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D021581:Active Transport, Cell Nucleus / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D030781:Organisms, Genetically Modified; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D046249:Transfer RNA Aminoacylation
C102145:ARC1 protein, S cerevisiae; D002352:Carrier Proteins; C518290:Cex1 protein, S cerevisiae; C408090:Los1 protein, S cerevisiae; C077730:NUP116 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D012343:RNA, Transfer