RNA editing in Drosophila 4f-rnp gene nuclear transcripts by multiple A-to-G conversions

Pre-mRNA editing results in production of transcripts having nucleotide sequences differing from that of the DNA template. We describe the first example of RNA editing in the fruitfly Drosophila melanogaster. This editing occurs in an alternatively spliced adult head transcript arising from the single-copy nuclear 4f-rnp gene via numerous A to G conversions. Editing sites were identified from comparisons of the genomic DNA sequence with that of corresponding cDNAs prepared from various developmental stages. We show that only the non-edited sequence is present in wild-type fly chromosomes, and have conducted a genetic rescue experiment that suggests that the edited cDNA is expressed in a protein that partially complements a lethal 4f-rnp mutation. The extensive editing observed is predicted to significantly alter the amino acid sequence of the encoded protein, and thus could provide a novel mechanism for the modulation of gene expression in Drosophila. The true significance of our discovery is that it was made in Drosophila, and the advantages of using Drosophila as a genetic model to further study RNA editing in the 4f-rnp gene are discussed.