The mouse prion promoter (containing 1140 bp of the prion protein gene upstream of exon 1, the complete exon 1, intron 1, and the first 52 bp of exon 2) drives the expression of the full-length human ATAXIN-3 (ATAXIN-3c isoform) containing 148 CAG repeats. To transport ATAXIN-3 into the cytoplasm, the nuclear export signal (NES) of the heat-stable inhibitor of the cAMP-dependent protein kinase was attached to ATAXIN-3. Five lines were created: NES.17, NES.24, NES.34, NES.40 and NES.42.