TDG is SUMOylated at lysine-330 with SUMO1 by UBE2I (Hardeland et al. 2002, Baba et al. 2005, Steinacher et al. 2005, Knipscheer et al. 2008, Smet-Nocca et al. 2011). Conjugation of SUMO1 to TDG induces dissociation of TDG from its product, an abasic site, and increases turnover of TDG with G:U substrate but abolishes activity with G:T substrate (Hardeland et al. 2002).