title: Two related trypanosomatid eIF4G homologues have functional differences compatible with distinct roles during translation initiation.
abstract: In higher eukaryotes, eIF4A, eIF4E and eIF4G homologues interact to enable mRNA recruitment to the ribosome. eIF4G acts as a scaffold for these interactions and also interacts with other proteins of the translational machinery. Trypanosomatid protozoa have multiple homologues of eIF4E and eIF4G and the precise function of each remains unclear. Here, 2 previously described eIF4G homologues, EIF4G3 and EIF4G4, were further investigated. In vitro, both homologues bound EIF4AI, but with different interaction properties. Binding to distinct eIF4Es was also confirmed; EIF4G3 bound EIF4E4 while EIF4G4 bound EIF4E3, both these interactions required similar binding motifs. EIF4G3, but not EIF4G4, interacted with PABP1, a poly-A binding protein homolog. Work in vivo with Trypanosoma brucei showed that both EIF4G3 and EIF4G4 are cytoplasmic and essential for viability. Depletion of EIF4G3 caused a rapid reduction in total translation while EIF4G4 depletion led to changes in morphology but no substantial inhibition of translation. Site-directed mutagenesis was used to disrupt interactions of the eIF4Gs with either eIF4E or eIF4A, causing different levels of growth inhibition. Overall the results show that only EIF4G3, with its cap binding partner EIF4E4, plays a major role in translational initiation.
authors.affiliation: a Centro de Pesquisas Aggeu Magalhães; Fundação Oswaldo Cruz ; Campus UFPE; Recife , PE , Brazil.
authors.forename: Danielle M N
authors.initials: DM
authors.lastname: Moura
authors.forename: Christian R S
authors.initials: CR
authors.lastname: Reis
authors.forename: Camila C
authors.initials: CC
authors.lastname: Xavier
authors.forename: Tamara D
authors.initials: TD
authors.lastname: da Costa Lima
authors.forename: Rodrigo P
authors.initials: RP
authors.lastname: Lima
authors.forename: Mark
authors.initials: M
authors.lastname: Carrington
authors.forename: Osvaldo P
authors.initials: OP
authors.lastname: de Melo Neto
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D039601:Eukaryotic Initiation Factor-4A / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D018320:Leishmania major / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010442:Peptide Chain Initiation, Translational; D039122:Poly(A)-Binding Protein I / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000378:metabolism
chemical_list: D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D039122:Poly(A)-Binding Protein I; D015800:Protozoan Proteins; D039601:Eukaryotic Initiation Factor-4A
keywords: GST, Glutathione-S-Transferase; HEAT domain, Huntingtin, elongation factor 3 (EF3); Leishmania major; MIF4G, Middle domain of eukaryotic Initiation Factor 4G; PABP, Poly(A) Binding Protein; Trypanosoma brucei; cap binding complex; eIF, eukaryotic Initiation Factor; protein phosphatase 2A (PP2A) and the yeast kinase TOR1; protein synthesis; translation initiation
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