title: Phenylalanyl-tRNA synthetase editing defects result in efficient mistranslation of phenylalanine codons as tyrosine.
abstract: Translational quality control is monitored at several steps, including substrate selection by aminoacyl-tRNA synthetases (aaRSs), and discrimination of aminoacyl-tRNAs by elongation factor Tu (EF-Tu) and the ribosome. Phenylalanyl-tRNA synthetase (PheRS) misactivates Tyr but is able to correct the mistake using a proofreading activity named editing. Previously we found that overproduction of editing-defective PheRS resulted in Tyr incorporation at Phe-encoded positions in vivo, although the misreading efficiency could not be estimated. This raised the question as to whether or not EF-Tu and the ribosome provide further proofreading mechanisms to prevent mistranslation of Phe codons by Tyr. Here we show that, after evading editing by PheRS, Tyr-tRNA(Phe) is recognized by EF-Tu as efficiently as the cognate Phe-tRNA(Phe). Kinetic decoding studies using full-length Tyr-tRNA(Phe) and Phe-tRNA(Phe), as well as a poly(U)-directed polyTyr/polyPhe synthesis assay, indicate that the ribosome lacks discrimination between Tyr-tRNA(Phe) and Phe-tRNA(Phe). Taken together, these data suggest that PheRS editing is the major proofreading step that prevents infiltration of Tyr into Phe codons during translation.
authors.affiliation: Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Jiqiang
authors.initials: J
authors.lastname: Ling
authors.forename: Srujana S
authors.initials: SS
authors.lastname: Yadavalli
authors.forename: Michael
authors.initials: M
authors.lastname: Ibba
mesh_terms: D003062:Codon / Q000378:metabolism*; D010441:Peptide Chain Elongation, Translational; D010444:Peptide Elongation Factor Tu / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism*; D010652:Phenylalanine-tRNA Ligase / Q000378:metabolism*; D017393:RNA Editing / Q000502:physiology*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism*