Evaluation of the involvement of eIF5A in the secretory pathway in Saccharomyces cerevisiae

Abstract

The probable translation initiation factor 5A (eIF5A) is highly conserved from archaea to mammals and undergoes a post-translational modification unique and essential called hipusination. Although the function of eIF5A as a translation initiation factor has never been clearly demonstrated, recent results from our laboratory strengthen its involvement in protein synthesis and suggest that its role is more related to the elongation step of translation. Studies also related eIF5A with cell proliferation and transition G1/S cell cycle, suggesting its involvement in translation of specific proteins that act directly on cell cycle progression. Additionally, it was shown that TIF51A is synthetically lethal with the gene YPT1, which encodes the protein Ypt1 responsible for vesicular transport of proteins from the Endoplasmic Reticulum (ER) to Golgi. The discovery of the genetic interaction between YPT1 and TIF51A suggests a connection between translation and the secretory pathway, essential for the process of budding and cell cycle progression in yeast. Moreover, recent data from our laboratory, unpublished, suggest the involvement of eIF5A in the secretory pathway by acting on the translocation of proteins to the ER via co-translational. To confirm this hypothesis, we intend to evaluate the role of eIF5A in the way of co-translational translocation, by tests of genetic interactions between TIF51A mutants and mutants of genes that encoding proteins that act in this way, for example mutants of the Sec complex (translocon), SRP (Signal Recognition Particle) and SRP´s receptors located in the ER membrane. In addition, we intend to conduct trials of co-purification of ribosomes associated with the translation machinery components, trying to analyze the differences between the wild and those strains that have mutations in the gene for eIF5A. Finally, it proposes to carry out proteomic analysis of cell wall components for mutants of eIF5A and deoxy-hipusine synthase, comparing the protein content of the wall of these mutants with that of the wild strain, so to better understand the phenotypes of mutants and how hipusinated eIF5A affects the translation associated with the secretory pathway. (AU)