Primary antibodies were: polyclonal sheep anti-huntingtin S830 (1:500, gift of Dr. G. Bates); rabbit polyclonal anti-Htt CAG53b (1:5000, gift of Erich Wanker); monoclonal anti-Htt mEM48 (1:200, Chemicon MAB5374); rabbit polyclonal anti-SUMO-1 (1:500, Santa Cruz FL101), and mouse monoclonal anti-human SUMO-1 (aa 1-101, Santa Cruz).