title: eIF4F-like complexes formed by cap-binding homolog TbEIF4E5 with TbEIF4G1 or TbEIF4G2 are implicated in post-transcriptional regulation in Trypanosoma brucei.
abstract: Members of the eIF4E mRNA cap-binding family are involved in translation and the modulation of transcript availability in other systems as part of a three-component complex including eIF4G and eIF4A. The kinetoplastids possess four described eIF4E and five eIF4G homologs. We have identified two new eIF4E family proteins in Trypanosoma brucei, and define distinct complexes associated with the fifth member, TbEIF4E5. The cytosolic TbEIF4E5 protein binds cap 0 in vitro. TbEIF4E5 was found in association with two of the five TbEIF4Gs. TbIF4EG1 bound TbEIF4E5, a 47.5-kDa protein with two RNA-binding domains, and either the regulatory protein 14-3-3 II or a 117.5-kDa protein with guanylyltransferase and methyltransferase domains in a potentially dynamic interaction. The TbEIF4G2/TbEIF4E5 complex was associated with a 17.9-kDa hypothetical protein and both 14-3-3 variants I and II. Knockdown of TbEIF4E5 resulted in the loss of productive cell movement, as evidenced by the inability of the cells to remain in suspension in liquid culture and the loss of social motility on semisolid plating medium, as well as a minor reduction of translation. Cells appeared lethargic, as opposed to compromised in flagellar function per se. The minimal use of transcriptional control in kinetoplastids requires these organisms to implement downstream mechanisms to regulate gene expression, and the TbEIF4E5/TbEIF4G1/117.5-kDa complex in particular may be a key player in that process. We suggest that a pathway involved in cell motility is affected, directly or indirectly, by one of the TbEIF4E5 complexes.
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Eden R
authors: ER
authors: Freire
authors: Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Ajay A
authors: AA
authors: Vashisht
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA Department of Microbiology, Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Recife, Pernambuco 50670-420, Brazil.
authors: Amaranta M
authors: AM
authors: Malvezzi
authors: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland.
authors: Joanna
authors: J
authors: Zuberek
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Gerasimos
authors: G
authors: Langousis
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Edwin A
authors: EA
authors: Saada
authors: Department of Microbiology, Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Recife, Pernambuco 50670-420, Brazil.
authors: Janaína De F
authors: Jde F
authors: Nascimento
authors: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland.
authors: Janusz
authors: J
authors: Stepinski
authors: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland Centre of New Technologies, University of Warsaw, 02-089 Warsaw, Poland.
authors: Edward
authors: E
authors: Darzynkiewicz
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Kent
authors: K
authors: Hill
authors: Department of Microbiology, Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Recife, Pernambuco 50670-420, Brazil.
authors: Osvaldo P
authors: OP
authors: De Melo Neto
authors: Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: James A
authors: JA
authors: Wohlschlegel
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: Nancy R
authors: NR
authors: Sturm
authors: Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors: David A
authors: DA
authors: Campbell
mesh_terms: D000595:Amino Acid Sequence; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry / Q000378:metabolism*; D039603:Eukaryotic Initiation Factor-4G / Q000378:metabolism*; D055786:Gene Knockout Techniques; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D039381:RNA Cap-Binding Proteins / Q000378:metabolism*; D012315:RNA Caps / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D016053:RNA, Protozoan / Q000378:metabolism; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*
chemical_list: D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D016053:RNA, Protozoan
keywords: 14-3-3 protein; kinetoplastid; mRNA cap; social motility; translation initiation factor