A-to-I RNA editing and the autorecoding sites in the Adar gene. (A) Chemical structure of adenosine, inosine, and guanosine and the process of A-to-I RNA editing mediated by the ADAR enzyme. In insects, there is a single copy of the Adar gene. (B) Adar autoregulatory pathway in Drosophila melanogaster. The autorecoding site in flies changes a Ser to a Gly, termed S > G site. (C) Convergent evolution of Adar autorecoding sites in flies and bees (Duan et al. 2021, 2022). Editing levels of each site are shown for each species. D. mel, Drosophila melanogaster; D. sim, Drosophila simulans; D. sec, Drosophila sechellia; D. ere, Drosophila erecta; B. ter, Bombus terrestris; A. mel, Apis mellifera. Editable Ser codons (at the first position) include AGT/C. Uneditable Ser codons (at the first position) include TCN (N = A/C/G/T). Editable Ile codon (at the third position) includes ATA. Uneditable Ile codons (at the third position) include ATC/T. (D) Domains and structures of Adar protein in D. melanogaster and A. mellifera. The positions of the two autorecoding sites, namely site1 and site2, are labeled in the figure.
