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Title: The unique Leishmania EIF4E4 N-terminus is a target for multiple phosphorylation events and participates in critical interactions required for translation initiation
Authors: de Melo Neto, Osvaldo P.
da Costa Lima, Tamara D. C.
Xavier, Camila C.
Nascimento, Larissa M.
Romão, Tatiany P.
Assis, Ludmila A.
Pereira, Mariana M. C.
Reis, Christian R. S.
Papadopoulou, Barbara
Affilliation: Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, Brasil
Abstract: The eukaryotic initiation factor 4E (eIF4E) recognizes the mRNA cap structure and, together with eIF4G and eIF4A, form the eIF4F complex that regulates translation initiation in eukaryotes. In trypanosomatids, 2 eIF4E homologues (EIF4E3 and EIF4E4) have been shown to be part of eIF4F-like complexes with presumed roles in translation initiation. Both proteins possess unique N-terminal extensions, which can be targeted for phosphorylation. Here, we provide novel insights on the Leishmania infantum EIF4E4 function and regulation. We show that EIF4E4 is constitutively expressed throughout the parasite development but is preferentially phosphorylated in exponentially grown promastigote and amastigote life stages, hence correlating with high levels of translation. Phosphorylation targets multiple serine-proline or threonine-proline residues within the N-terminal extension of EIF4E4 but does not require binding to the EIF4E4's partner, EIF4G3, or to the cap structure. We also report that EIF4E4 interacts with PABP1 through 3 conserved boxes at the EIF4E4 N-terminus and that this interaction is a prerequisite for efficient EIF4E4 phosphorylation. EIF4E4 is essential for Leishmania growth and an EIF4E4 null mutant was only obtained in the presence of an ectopically provided wild type gene. Complementation for the loss of EIF4E4 with several EIF4E4 mutant proteins affecting either phosphorylation or binding to mRNA or to EIF4E4 protein partners revealed that, in contrast to other eukaryotes, only the EIF4E4-PABP1 interaction but neither the binding to EIF4G3 nor phosphorylation is essential for translation. These studies also demonstrated that the lack of both EIF4E4 phosphorylation and EIF4G3 binding leads to a non-functional protein. Altogether, these findings further highlight the unique features of the translation initiation process in trypanosomatid protozoa.
Keywords: Amino Acid Motifs
Amino Acid Sequence
cap binding protein
Conserved Sequence
Eukaryotic Initiation Factor-4E
Eukaryotic Initiation Factor-4G
Gene Expression
Gene Knockout Techniques
Life Cycle Stages
Molecular Sequence Data
Peptide Chain Initiation, Translational
Poly(A)-Binding Proteins
Protein Binding
Protein Interaction Domains and Motifs
protein synthesis
Sequence Alignment
translation initiation PABP
keywords: Fator de Iniciação 4E em Eucariotos
Iniciação Traducional da Cadeia Peptídica
Domínios e Motivos de Interação entre Proteínas
DeCS: Fator de Iniciação 4E em Eucariotos
crescimento & desenvolvimento
Domínios e Motivos de Interação entre Proteínas
Iniciação Traducional da Cadeia Peptídica
Motivos de Aminoácidos
Sequência de Aminoácidos
Sequência Conservada
Expressão Gênica
Técnicas de Inativação de Genes
Estágios do Ciclo de Vida
Dados de Sequência Molecular
Proteínas de Ligação a Poli(A)
Ligação Proteica
Alinhamento de Sequência
Issue Date: 2015
Citation: DE MELO NETO, O. P. et al. The unique Leishmania EIF4E4 N-terminus is a target for multiple phosphorylation events and participates in critical interactions required for translation initiation. RNA biology, v. 12, n. 11, p. 1209–1221, 2015.
DOI: 10.1080/15476286.2015.1086865
ISSN: 1555-8584
Copyright: open access
Appears in Collections:PE - IAM - Artigos de Periódicos

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