Investigation of the interactions between eIF5A and translational machinery and the Ribosome Quality Control complex, using Saccharomyces cerevisiae as model organism.

Author(s)

Paulo Eduardo Gonçalves Boldrin

• Document type: Doctoral Thesis
• Press: Araraquara. 2016-03-15.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Farmacêuticas. Araraquara
• Defense date: 2016-02-22
• Advisor: Sandro Roberto Valentini; Cleslei Fernando Zanelli

Abstract

The translation factor 5A (eIF5A) is highly conserved and essential for cell viability. eIF5A is the only protein known to contain the essential amino acid residue hypusine, generated by a post-translational modification. Although eIF5A has been involved in different cellular pathways, recent studies have strengthened its role in protein synthesis, more specifically in the translation elongation step. Results of our group revealed a functional correlation between eIF5A and the Translation Elongation Factor 2 (eEF2). To further investigate the role of eIF5A in translation elongation, we carried out new experiments to study the physical interaction between eIF5A and eEF2. eIF5A does not interact directly with eEF2 and their physical interaction is dependent on ribosomal complexes. Moreover, eIF5A and eEF2 do not bind simultaneously to the same ribosome or they do not occupy the same ribosome for a long time. Additionally, as it was shown that the homolog of eIF5A in bacteria, EF-P, interacts physically with the Large Ribosome Protein 1 (L1). We evaluated a functional interaction between eIF5A and L1. The results demonstrated a strong genetic interaction between these factors and a possible dependency of L1 in the eIF5A ribosome binding. Finally, as eIF5A was recently involved in translation of polyproline stretches, which cause ribosome stalling, and other types of ribosome stalling recruit and activate the Ribosome Quality Control (RQC) complex, we also investigated the functional interaction between eIF5A and the RQC factors Ltn1 and Tae2. Although it was identified genetic interaction between mutants of eIF5A and mutants of these RQC factors, ribosome stalled at polyproline residues does not recruit the RQC complex. Curiously, it was observed that eIF5A is important for the formation of cellular aggregates caused by polylysines. Additionally, it was shown a correlation between normal levels of eIF5A in the cell and the presence of Sis1 e Cdc42 in the aggregates, suggesting a possible functional interaction between eIF5A and the RQC complex. (AU)

• FAPESP's process: 12/02305-0 - Study of the physical and functional interactions between eIF5A and the translation machinery using Saccharomyces cerevisiae as a model organismo
• Grantee: Paulo Eduardo Gonçalves Boldrin
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)