title: SUI1/p16 is required for the activity of eukaryotic translation initiation factor 3 in Saccharomyces cerevisiae.
abstract: A genetic reversion analysis at the HIS4 locus in Saccharomyces cerevisiae has identified SUI1 as a component of the translation initiation complex which plays an important role in ribosomal recognition of the initiator codon. SUI1 is an essential protein of 12.3 kDa that is required in vivo for the initiation of protein synthesis. Here we present evidence that SUI1 is identical to the smallest subunit, p16, of eukaryotic translation initiation factor 3 (eIF-3) in S. cerevisiae. SUI1 and eIF3-p16 comigrate upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis and cross-react with anti-SUI1 and anti-eIF3 antisera. Anti-SUI1 antisera immunoprecipitate all of the subunits of eIF3, whereas antisera against the eIF3 complex and the individual PRT1 and GCD10 subunits of eIF3 immunoprecipitate SUI1. Finally, the N-terminal amino acid sequence of a truncated form of eIF3-p16 matches the sequence of SUI1. eIF3 isolated from a sui1(ts) strain at 37 degrees C lacks SUI1 and fails to exhibit eIF3 activity in the in vitro assay for methionyl-puromycin synthesis. A free form of SUI1 separate from the eIF3 complex is found in S. cerevisiae but lacks activity in the in vitro assay. The results, together with prior genetic experiments, indicate that SUI1 is essential for eIF3 activity and functions as part of eIF3 and in concert with eIF2 to promote eIF2-GTP-Met-tRNAi ternary complex recognition of the initiator codon.
authors.affiliation: Department of Biological Chemistry, School of Medicine, University of California, Davis, 95616, USA.
authors.forename: T
authors.initials: T
authors.lastname: Naranda
authors.forename: S E
authors.initials: SE
authors.lastname: MacMillan
authors.forename: T F
authors.initials: TF
authors.lastname: Donahue
authors.forename: J W
authors.initials: JW
authors.lastname: Hershey
mesh_terms: D000429:Alcohol Oxidoreductases; D000595:Amino Acid Sequence; D000619:Aminohydrolases; D004591:Electrophoresis, Polyacrylamide Gel; D015977:Eukaryotic Initiation Factor-1; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D005800:Genes, Fungal; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011755:Pyrophosphatases; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D015977:Eukaryotic Initiation Factor-1; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; D046911:Macromolecular Substances; D010448:Peptide Initiation Factors; C072076:SUI1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000429:Alcohol Oxidoreductases; C092116:HIS4 protein, S cerevisiae; D000619:Aminohydrolases; D011755:Pyrophosphatases