UASt regulatory sequences drive expression of cDNA encoding the Adar 3/4 isoform that has been mutated to produce a non-editable mRNA; the codon encoding the Ser residue in exon 7 close to the active site which is normally edited by the Adar protein has been mutated to another Ser codon that does not have an A at the first position (codon is changed from AGT to TCT). The coding region is tagged with both Tag:FLAG and Tag:polyHis.