Editing is directed by a specific sequence surrounding the editing nucleotide. (a) An illustration showing the positions that were mutated in the Alu-exon (AEx) and the antisense intronic AluS (AluS): the flanking nucleotides of the edited E1 site, and the position in the antisense Alu that is predicted to be opposite to the E1 in the dsRNA formation. (b) Chromas sequences of the Alu-exon editing of the wild-type (WT) and three mutants from (a). WT and mutant plasmids were introduced into 293T cells by transfection, total RNA was extracted, and splicing products were separated on 1.5% agarose gel following RT-PCR analysis. The Alu-exon inclusion of the WT and mutants is highly similar (not shown). The edited positions are highlighted in black. (c) Rounded editing frequencies of each of the five edited sites, from three separate experiments, were quantified using the Discovery Studio Gene 1.5 program.