eIF5A interacts functionally with eEF2
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eIF5A is highly conserved from archaea to mammals, essential for cell viability and the only protein known to contain the essential amino acid residue hypusine, generated by a unique posttranslational modification. eIF5A was originally identified as a translation initiation factor due to its ability to stimulate the formation of the first peptide bond. However, recent studies have shown that depletion of eIF5A causes a significant decrease in polysome run-off and an increase in the ribosome transit time, suggesting that eIF5A is actually involved in the elongation step of protein synthesis. We have previously shown that the depletion mutant tif51A-3 (eIF5AC39Y/G118D) shows a sicker phenotype when combined with the dominant negative mutant eft2 H699K of the elongation factor eEF2. In this study, we used the eIF5AK56A mutant to further investigate the relationship between eIF5A and eEF2. The eIF5AK56A mutant is temperature sensitive and has a defect in protein synthesis, but instead of causing depletion of the eIF5A protein, this mutant has a defect in hypusine modification. Like the mutant tif51A-3, the eIF5AK56A mutant is synthetic sick with the mutant eft2 H699K of eEF2. High-copy eEF2 not only improves cell growth of the eIF5AK56A mutant, but also corrects its increased cell size defect. Moreover, eEF2 suppression of the eIF5AK56A mutant is correlated with the improvement of total protein synthesis and with the increased resistance to the protein synthesis inhibitor hygromycin B. Finally, the polysome profile defect of the eIF5AK56A mutant is largely corrected by high-copy eEF2. Therefore, these results demonstrate that eIF5A is closely related to eEF2 function during translation elongation.
KeywordseIF5A Hypusine eEF2 Translation elongation
Eukaryotic translation initiation factor 5A
Eukaryotic translation elongation factor 2
Gene encoding eIF5A in yeast
Gene encoding eEF2 in yeast
Gene encoding protein kinase C in yeast
Human immunodeficiency virus
Counts per minute
This work was supported by grants to S.R.V. from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and PADC from Faculdade de Ciências Farmacêuticas, UNESP. We also thank FAPESP, CNPq and CAPES for fellowships awarded to most of the authors (C. A. O. D.; A. P. B. G.; D. R.; F. C. G. and T. F. W.).
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