Utp8p Is an Essential Intranuclear Component of the Nuclear tRNA Export Machinery of Saccharomyces cerevisiae

A yeast tRNA three-hybrid interaction approach and an in vivo nuclear tRNA export assay based on amber suppression was used to identify proteins that participate in the nuclear tRNA export process in Saccharomyces cerevisiae. One of the proteins identified by this strategy is Utp8p, an essential 80-...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-08, Vol.278 (34), p.32236-32245
Main Authors: Steiner-Mosonyi, Marta, Leslie, Deena M., Dehghani, Hesam, Aitchison, John D., Mangroo, Dev
Format: Article
Language:English
Subjects:
Base Sequence
Cell Nucleus - metabolism
DNA Primers
Nuclear Proteins - genetics
Nuclear Proteins - metabolism
Protein Transport
RNA, Fungal - metabolism
RNA, Transfer - metabolism
Saccharomyces cerevisiae - metabolism
Saccharomyces cerevisiae Proteins - genetics
Saccharomyces cerevisiae Proteins - metabolism
Selection, Genetic
Two-Hybrid System Techniques
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Summary:A yeast tRNA three-hybrid interaction approach and an in vivo nuclear tRNA export assay based on amber suppression was used to identify proteins that participate in the nuclear tRNA export process in Saccharomyces cerevisiae. One of the proteins identified by this strategy is Utp8p, an essential 80-kDa nucleolar protein that has been implicated in 18 S ribosomal RNA biogenesis. Our characterization indicated that the major function of Utp8p is in nuclear tRNA export. Like the S. cerevisiae Los1p and the mammalian exportin-t, which are proteins known to facilitate nuclear tRNA export, overexpression of Utp8p restored export of tRNAamTyr mutants defective in nuclear export. Furthermore, depletion of Utp8p blocked nuclear export of mature tRNAs derived from both intronless and intron-containing pre-tRNAs but did not affect tRNA and rRNA maturation, nuclear export of mRNA and ribosomes, or nuclear tRNA aminoacylation. Overexpression of Utp8p also alleviated nuclear retention of non-aminoacylated tRNATyr in a tyrosyl-tRNA synthetase mutant strain. Utp8p binds tRNA directly and saturably, indicating that it has a tRNA-binding site. Utp8p does not appear to function as a tRNA export receptor, because it does not shuttle between the nucleus and the cytoplasm. Taken together, the results suggest that Utp8p is an essential intranuclear component of the nuclear tRNA export machinery, which may channel tRNA to the various tRNA export pathways operating in S. cerevisiae.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M302779200