Lower GC-content in editing exons: implications for regulation by molecular characteristics maintained by selection.

We unexpectedly discover that there are much lower GC3 and GC-content and higher Gibbs free energy on editing exons than other exons in the Drosophila synaptotagmin I transcripts, which was further, confirmed statistically by others 47 experimentally-validated samples. Sequence alignment, Ks and Ka/Ks assays suggest that rapidly ascending purifying selection occur in editing exons which constrains nucleotide divergency. The presence of specific molecular characteristics such as lower GC-content in editing exons imply an unexpected requirement and are likely to direct RNA editing occurrence. Thus, relations between molecular characteristics of DNA, RNA editing and purifying selection might be present.