G. Hernández, M. Altmann, J. M. Sierra, H. Urlaub, R. Diez del Corral, P. Schwartz, & R. Rivera-Pomar (2005) Functional analysis of seven genes encoding eight translation initiation factor 4E (eIF4E) isoforms in Drosophila. Mech. Development 122, 529-543
	http://www.blackwellpublishing.com/febsabstracts2005/abstract.asp?id=41000

Functional analysis of seven genes encoding eight translation initiation factor 4E (eIF4E) isoforms in Drosophila.

Hernandez G, Altmann M, Sierra JM, Urlaub H, del Corral RD, Schwartz P, Rivera-Pomar R.

Max-Planck-Institut fur biophysikalische Chemie, Abt. Molekulare Biologie, Am Fassberg 11, Gottingen 37077, Germany. hgreco[at]gwdg.de

The Drosophila genome-sequencing project has revealed a total of seven genes encoding eight eukaryotic initiation factor 4E (eIF4E) isoforms. Four of them (eIF4E-1,2, eIF4E-3, eIF4E-4 and eIF4E-5) share exon/intron structure in their carboxy-terminal part and form a cluster in the genome. All eIF4E isoforms bind to the cap (m7GpppN) structure. All of them, except eIF4E-6 and eIF4E-8 were able to interact with Drosophila eIF4G or eIF4E-binding protein (4E-BP). eIF4E-1, eIF4E-2, eIF4E-3, eIF4E-4 and eIF4E-7 rescued a yeast eIF4E-deficient mutant in vivo. Only eIF4E-1 mRNAs and, at a significantly lower level, eIF4E3 and eIF4E-8 are expressed in embryos and throughout the life cycle of the fly. The transcripts of the remaining isoforms were detected from the third instar larvae onwards. This indicates the cap-binding activity relies mostly on eIF4E-1 during embryogenesis. This agrees with the proteomic analysis of the eIF4F complex purified from embryos and with the rescue of l(3)67Af, an embryonic lethal mutant for the eIF4E-1,2 gene, by transgenic expression of eIF4E-1. Overexpression of eIF4E-1 in wild-type embryos and eye imaginal discs results in phenotypic defects in a dose-dependent manner.