Isolation and characterization of the cDNA and the gene for eukaryotic translation initiation factor 4G from Drosophila melanogaster

Recent evidence supports the notion that the eukaryotic polypeptide chain initiation factor (eIF)4G plays a critical bridging role in coordinating other eIF involved in eukaryotic translation initiation. Here we report the isolation and characterization of a 5621-bp cDNA encoding Drosophila eIF4G. The longest ORF predicts a polypeptide of 1666 amino acids with a molecular mass of 183 940 Da and shares 25% amino acid identity with other eIF4G. The 5' untranslated region is 386 nucleotides long and contains seven AUG codons out of frame. The in vitro transcription/translation of the cDNA yielded a major polypeptide, which was specifically immunoprecipitated with an antibody against Drosophila eIF4G. This polypeptide has the same electrophoretic mobility as eIF4G purified from Drosophila melanogaster embryos. A conserved eIF4E-binding motif was found in Drosophila eIF4G. The gene maps at the 102E region of chromosome 4 and spans a genomic region of approximately 16 kb. It was found to contain 15 introns. A single RNA transcript of approximately 5.9 kb was detected by northern blotting of poly(A)-rich RNA prepared from Drosophila adults. The sequence upstream of the transcription initiation site lacks the consensus TATA box, but contains several sequences possibly involved in the regulation of transcription.