title: New insights into the incorporation of natural suppressor tRNAs at stop codons in Saccharomyces cerevisiae.
abstract: Stop codon readthrough may be promoted by the nucleotide environment or drugs. In such cases, ribosomes incorporate a natural suppressor tRNA at the stop codon, leading to the continuation of translation in the same reading frame until the next stop codon and resulting in the expression of a protein with a new potential function. However, the identity of the natural suppressor tRNAs involved in stop codon readthrough remains unclear, precluding identification of the amino acids incorporated at the stop position. We established an in vivo reporter system for identifying the amino acids incorporated at the stop codon, by mass spectrometry in the yeast Saccharomyces cerevisiae. We found that glutamine, tyrosine and lysine were inserted at UAA and UAG codons, whereas tryptophan, cysteine and arginine were inserted at UGA codon. The 5' nucleotide context of the stop codon had no impact on the identity or proportion of amino acids incorporated by readthrough. We also found that two different glutamine tRNA(Gln) were used to insert glutamine at UAA and UAG codons. This work constitutes the first systematic analysis of the amino acids incorporated at stop codons, providing important new insights into the decoding rules used by the ribosome to read the genetic code.
authors: Institut de Génétique et Microbiologie, Université Paris-Sud, UMR8621, 91400 Orsay, France.
authors: Sandra
authors: S
authors: Blanchet
authors: CNRS, Centre de Recherche de Gif, FRC3115, Imagif, 91198 Gif-sur-Yvette Cedex, France.
authors: David
authors: D
authors: Cornu
authors: CNRS, Centre de Recherche de Gif, FRC3115, Imagif, 91198 Gif-sur-Yvette Cedex, France.
authors: Manuela
authors: M
authors: Argentini
authors: Institut de Génétique et Microbiologie, Université Paris-Sud, UMR8621, 91400 Orsay, France CNRS, 91400 Orsay, France olivier.namy@igmors.u-psud.fr.
authors: Olivier
authors: O
authors: Namy
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000926:Anticodon; D018388:Codon, Terminator; D005982:Glutathione Transferase / Q000235:genetics / Q000302:isolation & purification; D010443:Peptide Chain Termination, Translational; D012344:RNA, Transfer, Ala / Q000378:metabolism; D012351:RNA, Transfer, Gln / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000926:Anticodon; D018388:Codon, Terminator; D012344:RNA, Transfer, Ala; D012351:RNA, Transfer, Gln; D005982:Glutathione Transferase