S-HDAg interacts with Ubc9 and SUMO1 in yeast two-hybrid assay. The growth of yeast strain AH109 cotransformed with GAL4-DBD plasmid DNA (pGBKT7−S-HDAg) and different GAL4-AD plasmid DNAs (pACT2-SUMO1, pACT2-SUMO2, pACT2-SUMO3, or pACT2-Ubc9) on SD medium is shown. Cotransformants were isolated on SD medium lacking tryptophan and leucine (−Trp−Leu; left plate) or on SD medium lacking tryptophan, leucine, adenine, and histidine (−Trp−Leu−Ade−His; right plate). The lower panel represents the isolated cotransformants in which the GAL4-AD plasmids were used for cotransformation. Vector, pACT2 plasmid without insert DNA; AH109, DNA-free transformation control.