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. For nuclear targeting of ATAXIN-3, three repeats of the nuclear localization signal from the SV40 T antigen were cloned at the C terminus of ATAXIN-3. Three lines were established: NLS.28, NLS.10, and NLS.37.