PIAS4 SUMOylates TP53BP1 with SUMO1 in response to double-strand breaks in DNA (Galanty et al. 2009, Impens et al. 2014). Overall, like TP53BP1, SUMO1,2,3, UBE2I, PIAS1 and PIAS4 are all observed to accumulate at double-strand breaks.
SUMO transferase activity of PIAS4 [nucleoplasm]