UASt regulatory sequences drive expression of cDNA encoding the Adar 3/4 isoform with a Ser to Gly mutation in exon 7, close to the active site (codon is changed from AGT to GGT). This mutation is in a codon that can normally undergo RNA editing (carried out by the Adar protein), and the protein produced corresponds to the form produced after RNA editing has occurred. The coding region is tagged with both Tag:FLAG and Tag:polyHis.