Rit1, a tRNA backbone-modifying enzyme that mediates initiator and elongator tRNA discrimination

Cell. 1994 Nov 4;79(3):535-46. doi: 10.1016/0092-8674(94)90262-3.


Using a genetic screen in yeast aimed at identifying cellular factors involved in initiator and elongator methionine tRNA discrimination in the translational process, we have identified a mutation that abolish the requirement for elongator methionine tRNA. The gene affected, which we call the ribosylation of the initiator tRNA gene or RIT1, encodes a 2'-O-ribosyl phosphate transferase. This enzyme modifies exclusively the initiator tRNA in position 64 using 5'-phosphoribosyl-1'-pyrophosphate as the modification donor. As the initiator tRNA participates both in the initiation and elongation of translation in a rit1 strain, we conclude that the 2'-O-ribosyl phosphate modification discriminates the initiator tRNAs from the elongator tRNAs during protein synthesis. The modification enzyme was shown to recognize the stem-loop IV region that is unique in eukaryotic cytoplasmic initiator tRNAs.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Base Sequence
  • Chromosomes, Fungal
  • Cloning, Molecular
  • Molecular Sequence Data
  • Mutagenesis
  • Nucleic Acid Conformation
  • Pentosyltransferases / genetics*
  • Pentosyltransferases / metabolism*
  • Peptide Chain Elongation, Translational
  • Peptide Chain Initiation, Translational
  • Peptide Elongation Factor 1
  • Peptide Elongation Factors / metabolism
  • Protein Biosynthesis*
  • RNA Processing, Post-Transcriptional*
  • RNA, Transfer, Met / metabolism*
  • Restriction Mapping
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Selection, Genetic
  • Sequence Analysis, DNA
  • Substrate Specificity


  • Peptide Elongation Factor 1
  • Peptide Elongation Factors
  • RNA, Transfer, Met
  • Saccharomyces cerevisiae Proteins
  • Pentosyltransferases
  • RIT1 protein, S cerevisiae

Associated data

  • GENBANK/X80795