The protein known as eIF5A (eukaryotic initiation factor 5A) has an elusive role in translation. It has a unique and essential hypusine modification at a conserved lysine residue in most eukaryotes. In addition, this protein is modified by phosphorylation with unknown functions. In the present study we show that a phosphorylated state of eIF5A predominates in exponentially growing Trypanosoma cruzi cells, and extensive dephosphorylation occurs in cells in stationary phase. Phosphorylation occurs mainly at Ser2, as shown in yeast eIF5A. In addition, a novel phosphorylation site was identified at Tyr21. In exponential cells, T. cruzi eIF5A is partially associated with polysomes, compatible with a proposed function as an elongation factor, and becomes relatively enriched in polysomal fractions in stationary phase. Overexpression of the wild-type eIF5A, or eIF5A with Ser2 replaced by an aspartate residue, but not by alanine, increases the rate of cell proliferation and protein synthesis. However, the presence of an aspartate residue instead of Ser2 is toxic for cells reaching the stationary phase, which show a less-pronounced protein synthesis arrest and a decreased amount of eIF5A in dense fractions of sucrose gradients. We conclude that eIF5A phosphorylation and dephosphorylation cycles regulate translation according to the growth conditions.
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Research Article|
March 28 2013
Eukaryotic initiation factor 5A dephosphorylation is required for translational arrest in stationary phase cells
Janete Chung;
Janete Chung
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669 L6A, São Paulo, S.P. 04039-032, Brazil
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Antonio A. Rocha;
Antonio A. Rocha
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669 L6A, São Paulo, S.P. 04039-032, Brazil
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Renata R. Tonelli;
Renata R. Tonelli
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669 L6A, São Paulo, S.P. 04039-032, Brazil
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Beatriz A. Castilho;
Beatriz A. Castilho
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669 L6A, São Paulo, S.P. 04039-032, Brazil
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Sergio Schenkman
Sergio Schenkman
1
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669 L6A, São Paulo, S.P. 04039-032, Brazil
1To whom correspondence should be addressed (email sschenkman@unifesp.br).
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Publisher: Portland Press Ltd
Received:
October 08 2012
Revision Received:
January 24 2013
Accepted:
January 31 2013
Accepted Manuscript online:
January 31 2013
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2013 Biochemical Society
2013
Biochem J (2013) 451 (2): 257–267.
Article history
Received:
October 08 2012
Revision Received:
January 24 2013
Accepted:
January 31 2013
Accepted Manuscript online:
January 31 2013
Citation
Janete Chung, Antonio A. Rocha, Renata R. Tonelli, Beatriz A. Castilho, Sergio Schenkman; Eukaryotic initiation factor 5A dephosphorylation is required for translational arrest in stationary phase cells. Biochem J 15 April 2013; 451 (2): 257–267. doi: https://doi.org/10.1042/BJ20121553
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