The eukaryotic translation initiation factor 5A (EIF5A) protein is highly conserved in eukaryotes. Some studies have shown that eIF5A has important roles in cell proliferation control and HIV-1 replication. EIF5A possesses a particular amino acid residue named hypusine that is not found in others proteins. The hypusine is essential for its activity and is produced by a post-translational modification using spermidine as substrate. Recent studies have demonstrated that EIF5A and the orthologous protein in bacteria (EFP) are involved in the translation of sequences that have three or more consecutive proline residues. Proteins with proline-rich regions are commonly found in prokaryotes and eukaryotes. The S6K2 protein has a region with five consecutives prolines in its C-terminus. The S6Ks proteins are responsible for phosphorylating the ribosomal protein S6 (rpS6) and this activation is essential for protein synthesis and cell cycle progression. Some authors indicate that the proline-rich region may be part of a regulatory mechanism through interactions between proteins, however, there are no reports demonstrating this mechanism for S6K2. In this project will be evaluated the involvement of EIF5A in translation of S6Ks, seeking a greater understanding of this regulation.
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