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Protein synthesis in eukaryotes


Protein synthesis in eukaryotes is regulated mainly through the activities of the initiation factors elF2 and eIF4F. elF2 is a heterotrimer, with the a subunit playing a regulatory role. Its phosphorylation by specific kinases results in inhibition of translation. The B subunit mediares interactions with other translation initiation components, and stabilizes the binding of GTP to the eIF2 complex; the y subunit, due to its similarity to EF- Tu, might bind GTP and the initiator tRNA. GCN2, the only eIF2a kinase found in the yeast S. cerevisiae, is activated by the binding of uncharged tRNA ' s. In mammals, besides GCN2, three other eIF2a kinases are known: PKR, HRI and PERK, activated by dsRNA, lack of hemin and endoplasmic reticulum stress, respectively. eIF4F, also a heterotrimeric factor, is responsible for the coupling of the 43S complex to the 5' end of mRNA ' s through the direct binding of its eIF4E subunit to the cap. eIF4E can be sequestered away from this interaction through its binding to 4E-BP, an interaction that is regulated by the phosphorylation of 4E-BP by mTOR. The activity of these factors, besides controlling general protein synthesis, can lead to the differential translation of rnRNA 's, thus representing mechanisms for adjusting the synthesis of specific proteins to the immediate needs of cells, independently of transcriptional regulation. This project will address the function and regulation of eIF2 and eIF4E in S. cerevisiae, in trypanosomatids and mammals, focusing on the following specific aspects: functional study of the beta subunit of eIF2, in yeast -analysis of the association of eIF2B with eIF2y, and determination of the function of the C2C2 region of eIF2B. GCN2-dependent translational regulation, in yeast - determination of the function of proteins encoded by ORF's YDR152W and YLR419W, which share conserved sequences with the N-terminus of GCN2. Translational regulation in trypanosomatids -studies on the phosphorylation of eIF2a, and characterization of eIF4E. Translational regulation in the mammalian brain -mechanism of translation regulation in the experimental model of epilepsy; determination of the expression of GCN1 and GCN2 in brain; study of the function of the protein Impact, which shares conserved sequences with the N-terminus of GCN2. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DE OLIVEIR, JULIANA FERREIRA; CASTILHO, BEATRIZ A.; SFORCA, MAURICIO L.; KRIEGER, MARCO AURELIO; ZERI, ANA CAROLINA; GUIMARAES, BEATRIZ G.; ZANCHIN, NILSON I. T.. Characterization of the Trypanosoma cruzi ortholog of the SBDS protein reveals an intrinsically disordered extended C-terminal region showing RNA-interacting activity. Biochimie, v. 91, n. 4, p. 475-483, . (02/12597-7, 00/10266-8, 98/14138-2)
ROFFE, MARTIN; BERALDO, FLAVIO HENRIQUE; BESTER, ROMINA; NUNZIANTE, MAX; BACH, CHRISTIAN; MANCINI, GABRIEL; GILCH, SABINE; VORBERG, INA; CASTILHO, BEATRIZ A.; MARTINS, VILMA REGINA; et al. Prion protein interaction with stress-inducible protein 1 enhances neuronal protein synthesis via mTOR. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, v. 107, n. 29, p. 13147-13152, . (02/12597-7)

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