Rit1, a tRNA backbone-modifying enzyme that mediates initiator and elongator tRNA discrimination.
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.
Aström
S U
SU
Department of Microbiology, University of Umeå, Sweden.
Byström
A S
AS
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009690:Nucleic Acid Conformation; D010430:Pentosyltransferases / Q000235:genetics* / Q000378:metabolism*; D010441:Peptide Chain Elongation, Translational; D010442:Peptide Chain Initiation, Translational; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000378:metabolism; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D012358:RNA, Transfer, Met / Q000378:metabolism*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins; D010430:Pentosyltransferases; C090456:RIT1 protein, S cerevisiae