The influence of 5' codon context on translation termination in Saccharomyces cerevisiae.
Translation termination in vivo was studied in the yeast Saccharomyces cerevisiae using a translation-assay system. Codon changes that were made at position -2 relative to the stop codon, gave a 3.5-fold effect on termination in a release-factor-defective (sup45) mutant strain, in line with the effect observed in a wild-type strain. The influence of the -2 codon could be correlated to the charge of the corresponding amino acid residue in the nascent peptide; an acidic residue favoring efficient termination. Thus, the C-terminal end of the nascent peptide influences translation termination both in the bacterium Escherichia coli and to a lesser extent in the yeast S. cerevisiae. However, the sensitivity to the charge of the penultimate amino acid is reversed when the E. coli and S. cerevisiae are compared. Changing - 1 (P-site) codons in yeast gave a 10-fold difference in effect on the efficiency of termination. This effect could not be related to any property of the encoded last amino acid in the nascent peptide. Iso-codons read by the same tRNA (AAA/G, GAA/G) gave similar readthrough values. Codons for glutamine (CAA/G), glutamic acid (GAA/G) and isoleucine (AUA/C) that are read by different isoaccepting tRNAs are associated with an approximately twofold difference in each case in termination efficiency. This suggests that the P-site tRNA is able to influence termination at UGAC in yeast.
Mottagui-Tabar
S
S
Department of Biosciences, University of Kent at Canterbury, United Kingdom.
Tuite
M F
MF
Isaksson
L A
LA
D001483:Base Sequence; D018388:Codon, Terminator; D004926:Escherichia coli / Q000235:genetics; D014176:Protein Biosynthesis; D012331:RNA, Fungal / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013205:Staphylococcal Protein A / Q000235:genetics
D018388:Codon, Terminator; D012331:RNA, Fungal; D013205:Staphylococcal Protein A; D012343:RNA, Transfer