title: Budding yeast GCN1 binds the GI domain to activate the eIF2alpha kinase GCN2.
abstract: When starved for a single amino acid, the budding yeast Saccharomyces cerevisiae activates the eukaryotic initiation factor 2alpha (eIF2alpha) kinase GCN2 in a GCN1-dependent manner. Phosphorylated eIF2alpha inhibits general translation but selectively derepresses the synthesis of the transcription factor GCN4, which leads to coordinated induction of genes involved in biosynthesis of various amino acids, a phenomenon called general control response. We recently demonstrated that this response requires binding of GCN1 to the GI domain occurring at the N terminus of GCN2 (Kubota, H., Sakaki, Y., and Ito, T. (2000) J. Biol. Chem. 275, 20243-20246). Here we provide the first evidence for the involvement of GCN1-GCN2 interaction in activation of GCN2 per se. We identified a C-terminal segment of GCN1 sufficient to bind the GI domain and used a novel dual bait two-hybrid method to identify mutations rendering GCN1 incapable of interacting with GCN2. The yeast bearing such an allele, gcn1-F2291L, fails to display derepression of GCN4 translation and hence general control response, as does a GI domain mutant, gcn2-Y74A, defective in association with GCN1. Furthermore, we demonstrated that phosphorylation of eIF2alpha is impaired in both mutants. Since GCN2 is the sole eIF2alpha kinase in yeast, these findings indicate a critical role of GCN1-GCN2 interaction in activation of the kinase in vivo.
authors.affiliation: Division of Genome Biology, Cancer Research Institute, Kanazawa University, 13-1 Takaramachi, Kanazawa 920-0934, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kubota
authors.forename: K
authors.initials: K
authors.lastname: Ota
authors.forename: Y
authors.initials: Y
authors.lastname: Sakaki
authors.forename: T
authors.initials: T
authors.lastname: Ito
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005838:Genotype; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010445:Peptide Elongation Factors; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D004268:DNA-Binding Proteins; D015852:Eukaryotic Initiation Factor-2; D005656:Fungal Proteins; C501389:GCN1 protein, S cerevisiae; D010445:Peptide Elongation Factors; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C512912:GCN2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases