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Exceptional codon recognition by the glutamine tRNAs in Saccharomyces cerevisiae
1Laboratory of Genetics, University of Wisconsin, Madison 53706.
The EMBO Journal
|June 1, 1991
Summary
Mutant glutamine tRNAs in yeast severely limit growth, revealing unique codon recognition. These findings suggest potential applications for expressing genes with unusual codons in protozoa.
Area of Science:
- Molecular Biology
- Genetics
- Yeast Biology
Background:
- Wild-type glutamine tRNAs in yeast exhibit low-level nonsense suppression.
- Increasing glutamine tRNA gene copy number enhances this suppression.
- The sup70 gene in yeast codes for glutamine tRNA(CAG).
Purpose of the Study:
- To further investigate glutamine tRNA behavior and codon recognition.
- To identify anticodon mutations in the yeast sup70 gene conferring nonsense suppression.
- To explore the potential applications of yeast glutamine tRNA suppressors.
Main Methods:
- Identification of anticodon mutations in the yeast sup70 gene.
- Analysis of a sup70 deletion to assess growth limitations.
- In vivo over-expression of glutamine tRNA(CAA) to study codon translation.
Main Results:
- Mutations in sup70 confer nonsense suppression but severely limit yeast growth.
- Growth limitation is due to the loss of wild-type glutamine tRNA(CAG) function.
- Amber suppressor glutamine tRNA(UAG) can inefficiently translate 5'-CAG-3' codons via a two-out-of-three reading mechanism.
- Over-expressed glutamine tRNA(CAA) translates 5'-CAG-3' codons using a prokaryotic-like U/G wobble mechanism.
Conclusions:
- Yeast glutamine tRNA suppressors exhibit unusual codon recognition properties.
- These suppressors could be utilized to express ciliated protozoan genes containing internal 5'-UAG-3' and 5'-UAA-3' codons.