Effect of initiation factor eIF-5A depletion on protein synthesis and proliferation of Saccharomyces cerevisiae

• Published in: The Journal of biological chemistry Vol. 269; no. 6; pp. 3934 - 3940
• Main Authors: Kang, H A, Hershey, J W
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 11.02.1994
• Subjects: Base Sequence; Biological and medical sciences; Cell Division; Cell Survival; DNA Primers - chemistry; Eukaryotic Translation Initiation Factor 5A; Fundamental and applied biological sciences. Psychology; Fungal Proteins - metabolism; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Peptide Chain Initiation, Translational; Peptide Initiation Factors - metabolism; RNA-Binding Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - metabolism; Translation. Translation factors. Protein processing; Fungi; Cell proliferation; Immunoprecipitation reaction; Protein synthesis; Initiation factor eIF4D; Translation initiation; Ascomycetes; Mutation; Saccharomyces cerevisiae; Biological activity; Thallophyta
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(17)41723-6

Eukaryotic translation initiation factor eIF-5A (formerly eIF-4D) is thought to function in protein synthesis by promoting synthesis of the first peptide bond because it stimulates methionyl-puromycin formation in vitro. eIF-5A is encoded by two genes (TIF51A and TIF51B) in Saccharomyces cerevisiae; the protein and its hypusine modification are essential for cell viability. To analyze the factor's function in vivo, we expressed from the repressible GAL promoter a functional but unstable eIF-5A fusion protein (R-eIF-5A) with an NH2-terminal arginine which is subject to rapid turnover through the NH2-terminal end rule proteolytic pathway. When the conditional mutant strain is shifted from galactose to glucose medium, the rapid disappearance of R-eIF-5A protein occurs within one generation, causing an immediate inhibition of cell growth. However, eIF-5A-depleted cells synthesize protein at about 70% of the wild type rate and exhibit only a slight change in polysome profiles reflecting a subtle defect in a late step of translation initiation. These results suggest that the activity of eIF-5A may not be absolutely essential for general protein synthesis. Rather, eIF-5A may be selectively required for translation of certain mRNAs and/or may be involved in some other aspect of cell metabolism.