RARA (Retinoic acid receptor alpha) is SUMOylated at lysine-166, lysine-171, and lysine-399 with SUMO2 (Zhu et al. 2009). SUMOylation at lysine-166 and lysine-171 is induced by all-trans retinoic acid and inhibits nuclear localization of RARA. SUMOylation at lysine-399 is observed in the absence of all-trans retinoic acid and enhances nuclear localization of RARA. SUMOylation of all 3 sites inhibits transcriptional activation by RARA.