The CBX3 component of PRC1 SUMOylates CASP8AP2 (FLASH) at lysine-1813 with SUMO1 (Alm-Kristiansen et al. 2009). SUMOylation enhances the transcriptional coactivation activity of CASP8AP2. SUMOylation also appears to trigger proteasomal degradation of CASP8AP2 (Vennemann and Hofmann 2013).
SUMO transferase activity of PRC1 complex [nucleoplasm]