title: Ribosome-binding domain of eukaryotic initiation factor-2 kinase GCN2 facilitates translation control.
abstract: A family of protein kinases regulate translation initiation in response to cellular stresses by phosphorylation of eukaryotic initiation factor-2 (eIF-2). One family member from yeast, GCN2, contains a region homologous to histidyl-tRNA synthetases juxtaposed to the kinase catalytic domain. It is thought that uncharged tRNA accumulating during amino acid starvation binds to the synthetase-related sequences and stimulates phosphorylation of the alpha subunit of eIF-2. In this report, we define another domain in GCN2 that functions to target the kinase to ribosomes. A truncated version of GCN2 containing only amino acid residues 1467 to 1590 can independently associate with the translational machinery. Interestingly, this region of GCN2 shares sequence similarities with the core of the double-stranded RNA-binding domain (DRBD). Substitutions of the lysine residues conserved among DRBD sequences block association of GCN2 with ribosomes and impaired the ability of the kinase to stimulate translational control in response to amino acid limitation. Additionally, as found for other DRBD sequences, recombinant protein containing GCN2 residues 1467-1590 can bind double-stranded RNA in vitro, suggesting that interaction with rRNA mediates ribosome targeting. These results indicate that appropriate ribosome localization of the kinase is an obligate step in the mechanism leading to translational control by GCN2.
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202-5122, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhu
authors.forename: R C
authors.initials: RC
authors.lastname: Wek
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000378:metabolism*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D010448:Peptide Initiation Factors; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D011494:Protein Kinases; D019892:eIF-2 Kinase