title: Complex formation by all five homologues of mammalian translation initiation factor 3 subunits from yeast Saccharomyces cerevisiae.
abstract: The PRT1, TIF34, GCD10, and SUI1 proteins of Saccharomyces cerevisiae were found previously to copurify with eukaryotic translation initiation factor 3 (eIF3) activity. Although TIF32, NIP1, and TIF35 are homologous to subunits of human eIF3, they were not known to be components of the yeast factor. We detected interactions between PRT1, TIF34, and TIF35 by the yeast two-hybrid assay and in vitro binding assays. Discrete segments (70-150 amino acids) of PRT1 and TIF35 were found to be responsible for their binding to TIF34. Temperature-sensitive mutations mapping in WD-repeat domains of TIF34 were isolated that decreased binding between TIF34 and TIF35 in vitro. The lethal effect of these mutations was suppressed by increasing TIF35 gene dosage, suggesting that the TIF34-TIF35 interaction is important for TIF34 function in translation. Pairwise in vitro interactions were also detected between PRT1 and TIF32, TIF32 and NIP1, and NIP1 and SUI1. Furthermore, PRT1, NIP1, TIF34, TIF35, and a polypeptide with the size of TIF32 were specifically coimmunoprecipitated from the ribosomal salt wash fraction. We propose that all five yeast proteins homologous to human eIF3 subunits are components of a stable heteromeric complex in vivo and may comprise the conserved core of yeast eIF3.
authors.affiliation: Laboratory of Eukaryotic Gene Regulation, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: K
authors.initials: K
authors.lastname: Asano
authors.forename: L
authors.initials: L
authors.lastname: Phan
authors.forename: J
authors.initials: J
authors.lastname: Anderson
authors.forename: A G
authors.initials: AG
authors.lastname: Hinnebusch
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; C077915:NIP1 protein, S cerevisiae; D009687:Nuclear Proteins; D010448:Peptide Initiation Factors; C050998:Prt1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C102947:TIF34 protein, S cerevisiae; D014157:Transcription Factors