PIAS1,3 SUMOylates MBD1 at lysine-499 and lysine-538 of the reference sequence (lysine-450 and lysine-489 of isoform 5) with SUMO1 (Lyst et al. 2006, Uchimura et al. 2006). SUMOylated MBD1 does not form a complex with SETDB1 and does not repress transcription.
SUMO transferase activity of PIAS1,3 [nucleoplasm]