title: Two zebrafish eIF4E family members are differentially expressed and functionally divergent.
abstract: Eukaryotic translation initiation factor 4E (eIF4E) is an essential component of the translational machinery that binds m(7)GTP and mediates the recruitment of capped mRNAs by the small ribosomal subunit. Recently, a number of proteins with homology to eIF4E have been reported in plants, invertebrates, and mammals. Together with the prototypical translation factor, these constitute a new family of structurally related proteins. To distinguish the prototypical translation factor eIF4E from other family members, it has been termed eIF4E-1 (Keiper, B. D., Lamphear, B. J., Deshpande, A. M., Jankowska-Anyszka, M., Aamodt, E. J., Blumenthal, T., and Rhoads, R. E. (2000) J. Biol. Chem. 275, 10590-10596). We describe the characterization of two eIF4E family members in the zebrafish Danio rerio. Based on their relative identities with human eIF4E-1, these zebrafish proteins are termed eIF4E-1A (82%) and eIF4E-1B (66%). eIF4E-1B, originally termed eIF4E(L), has been reported previously as the zebrafish eIF4E-1 counterpart (Fahrenkrug, S. C., Dahlquist, M. O., Clark, K., and Hackett, P. B. (1999) Differentiation 65, 191-201; Fahrenkrug, S. C., Joshi, B., Hackett, P. B., and Jagus, R. (2000) Differentiation 66, 15-22). Sequence comparisons suggest that the two genes probably evolved from a duplication event that occurred during vertebrate evolution. eIF4E-1A is expressed ubiquitously in zebrafish, whereas expression of eIF4E-1B is restricted to early embryonic development and to gonads and muscle of the tissues investigated. The ability of these two zebrafish proteins to bind m(7)GTP, eIF4G, and 4E-BP, as well as to complement yeast conditionally deficient in functional eIF4E, show that eIF4E-1A is a functional equivalent of human eIF4E-1. Surprisingly, although eIF4E-1B possesses all known residues thought to be required for interaction with the cap structure, eIF4G, and 4E-BPs, it fails to interact with any of these components, suggesting that this protein serves a role other than that assigned to eIF4E.
authors.affiliation: Center of Marine Biotechnology, Baltimore, Maryland 21202, USA.
authors.forename: Javier
authors.initials: J
authors.lastname: Robalino
authors.forename: Bhavesh
authors.initials: B
authors.lastname: Joshi
authors.forename: Scott C
authors.initials: SC
authors.lastname: Fahrenkrug
authors.forename: Rosemary
authors.initials: R
authors.lastname: Jagus
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000096:biosynthesis* / Q000502:physiology*; D039642:Eukaryotic Initiation Factors / Q000378:metabolism; D005260:Female; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D010053:Ovary / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014981:Xenopus; D015027:Zebrafish
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; C087000:EIF4EBP1 protein, human; C104151:EIF4EBP2 protein, human; C112661:EIF4EBP3 protein, human; D039561:Eukaryotic Initiation Factor-4E; D039642:Eukaryotic Initiation Factors; D010750:Phosphoproteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D005982:Glutathione Transferase