PIAS4 SUMOylates HERC2 at an unknown lysine residue with SUMO1 (Danielsen et al. 2012). HERC2 binds SUMO1 and is then SUMOylated. SUMOylation of HERC2 promotes binding to RNF8 at double-strand breaks in DNA.
SUMO transferase activity of PIAS4 [nucleoplasm]