UAS regulatory sequences drive expression of a cDNA that encodes the Hsap\ATXN3 dominant isoform containing 3 ubiquitin-interacting motifs, which has been engineered to encode an expanded polyglutamine (polyQ) repeat of 80 residues (the polyQ repeats are encoded by CAGCAA repeats, rather than a pure CAG tract). Contains a mutation in ubiquitin-binding site 1 (UbS1) and mutations in the ubiquitin-interacting motifs (UIMs) to disable their interaction with ubiquitin chains.