A "gain of function" mutation in a protein mediates production of novel modified nucleosides

EMBO J. 2005 May 18;24(10):1842-51. doi: 10.1038/sj.emboj.7600666. Epub 2005 Apr 28.


The mutation sufY204 mediates suppression of a +1 frameshift mutation in the histidine operon of Salmonella enterica serovar Typhimurium and synthesis of two novel modified nucleosides in tRNA. The sufY204 mutation, which results in an amino-acid substitution in a protein, is, surprisingly, dominant over its wild-type allele and thus it is a "gain of function" mutation. One of the new nucleosides is 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U34) modified by addition of a C(10)H(17) side chain of unknown structure. Increased amounts of both nucleosides in tRNA are correlated to gene dosage of the sufY204 allele, to an increased efficiency of frameshift suppression, and to a decreased amount of the wobble nucleoside mnm(5)s(2)U34 in tRNA. Purified tRNA(Gln)(cmnm(5)s(2)UUG) in the mutant strain contains a modified nucleoside similar to the novel nucleosides and the level of aminoacylation of tRNA(Gln)(cmnm(5)s(2)UUG) was reduced to 26% compared to that found in the wild type (86%). The results are discussed in relation to the mechanism of reading frame maintenance and the evolution of modified nucleosides in tRNA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Substitution
  • Frameshift Mutation*
  • Genes, Suppressor*
  • Lac Operon / genetics
  • Nucleosides / biosynthesis*
  • Nucleosides / chemistry
  • Operon*
  • RNA, Transfer / chemistry
  • RNA, Transfer / genetics
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism
  • Selenic Acid
  • Selenium Compounds / metabolism
  • Spectrometry, Mass, Electrospray Ionization
  • Transfer RNA Aminoacylation / genetics
  • Transfer RNA Aminoacylation / physiology


  • Nucleosides
  • Selenium Compounds
  • RNA, Transfer
  • Selenic Acid