Expression of a specific mutant form of Ubiquitin-Like Modifier-Activating Enzyme 2 (Uba2), a SUMO-1 activating enzyme, was found to worsen the polyQ-AR mediated degeneration in SBMA fly model (Chan et al., 2002); however, it still remains unclear whether the effects of this Uba2 mutant (Uba2.C175S) on SBMA phenotypes are mediated by modulating AR SUMOylation. The gene discussed is UBA2; the disease is Kennedy disease.