Several nucleotide substitutions, resulting in amino acid substitutions R37A, H38G, and R39S, were introduced to disrupt the nuclear localization signal and the dioxin-responsive element (DRE) binding domain in exon 2. Also, a neomycin resistance gene cassette was introduced into intron 1 for positive selection. Western blot analysis confirmed expression of the mutant protein is similar that of wild-type. (J:83597)