title: Translation initiation requires cell division cycle 123 (Cdc123) to facilitate biogenesis of the eukaryotic initiation factor 2 (eIF2).
abstract: The eukaryotic translation initiation factor 2 (eIF2) is central to the onset of protein synthesis and its modulation in response to physiological demands. eIF2, a heterotrimeric G-protein, is activated by guanine nucleotide exchange to deliver the initiator methionyl-tRNA to the ribosome. Here we report that assembly of the eIF2 complex in vivo depends on Cdc123, a cell proliferation protein conserved among eukaryotes. Mutations of CDC123 in budding yeast reduced the association of eIF2 subunits, diminished polysome levels, and increased GCN4 expression indicating that Cdc123 is critical for eIF2 activity. Cdc123 bound the unassembled eIF2γ subunit, but not the eIF2 complex, and the C-terminal domain III region of eIF2γ was both necessary and sufficient for Cdc123 binding. Alterations of the binding site revealed a strict correlation between Cdc123 binding, the biological function of eIF2γ, and its ability to assemble with eIF2α and eIF2β. Interestingly, high levels of Cdc123 neutralized the assembly defect and restored the biological function of an eIF2γ mutant. Moreover, the combined overexpression of eIF2 subunits rescued an otherwise inviable cdc123 deletion mutant. Thus, Cdc123 is a specific eIF2 assembly factor indispensable for the onset of protein synthesis. Human Cdc123 is encoded by a disease risk locus, and, therefore, eIF2 biogenesis control by Cdc123 may prove relevant for normal cell physiology and human health. This work identifies a novel step in the eukaryotic translation initiation pathway and assigns a biochemical function to a protein that is essential for growth and viability of eukaryotic cells.
authors.affiliation: Department of Genetics, University of Regensburg, D-93040 Regensburg, Germany.
authors.forename: Angelika F
authors.initials: AF
authors.lastname: Perzlmaier
authors.forename: Frank
authors.initials: F
authors.lastname: Richter
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Seufert
mesh_terms: D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010442:Peptide Chain Initiation, Translational / Q000235:genetics; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000235:genetics*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; C493791:Cdc123 protein, S cerevisiae; D018797:Cell Cycle Proteins; D015852:Eukaryotic Initiation Factor-2; C501391:GCN4 protein, S cerevisiae; D021122:Protein Subunits; C584100:SUI2 protein, S cerevisiae; C584101:SUI3 protein, S cerevisiae; C584102:SUI4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C098828:CDC123 protein, human
keywords: Cdc123; Molecular Biology; Protein Assembly; Protein Synthesis; Protein-Protein Interactions; Translation Initiation; Translation Initiation Factors; Yeast Genetics; eIF2