Cbx4 (Pc2) sumoylates Dnmt3a with Sumo1 at more than one site in the N-terminal (regulatory) domain (Ling et al. 2004, Li et al. 2007). Sumoylation reduces the interaction of Dnmt3a with Hdac1 and Hdac2.
SUMO transferase activity of Cbx4 [nucleoplasm]