Genetic selection for mistranslation rescues a defective co-chaperone in yeast

Nucleic Acids Res. 2017 Apr 7;45(6):3407-3421. doi: 10.1093/nar/gkw1021.


Despite the general requirement for translation fidelity, mistranslation can be an adaptive response. We selected spontaneous second site mutations that suppress the stress sensitivity caused by a Saccharomyces cerevisiae tti2 allele with a Leu to Pro mutation at residue 187, identifying a single nucleotide mutation at the same position (C70U) in four tRNAProUGG genes. Linkage analysis and suppression by SUF9G3:U70 expressed from a centromeric plasmid confirmed the causative nature of the suppressor mutation. Since the mutation incorporates the G3:U70 identity element for alanyl-tRNA synthetase into tRNAPro, we hypothesized that suppression results from mistranslation of Pro187 in Tti2L187P as Ala. A strain expressing Tti2L187A was not stress sensitive. In vitro, tRNAProUGG (C70U) was mis-aminoacylated with alanine by alanyl-tRNA synthetase, but was not a substrate for prolyl-tRNA synthetase. Mass spectrometry from protein expressed in vivo and a novel GFP reporter for mistranslation confirmed substitution of alanine for proline at a rate of ∼6%. Mistranslating cells expressing SUF9G3:U70 induce a partial heat shock response but grow nearly identically to wild-type. Introducing the same G3:U70 mutation in SUF2 (tRNAProAGG) suppressed a second tti2 allele (tti2L50P). We have thus identified a strategy that allows mistranslation to suppress deleterious missense Pro mutations in Tti2.

MeSH terms

  • Alleles
  • Amino Acid Substitution*
  • Introns
  • Molecular Chaperones / biosynthesis
  • Molecular Chaperones / genetics*
  • Protein Biosynthesis*
  • RNA, Transfer, Pro / genetics*
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins / biosynthesis
  • Saccharomyces cerevisiae Proteins / genetics*
  • Selection, Genetic
  • Suppression, Genetic*


  • Molecular Chaperones
  • RNA, Transfer, Pro
  • Saccharomyces cerevisiae Proteins
  • Tti2 protein, S cerevisiae