E3 SUMO-protein ligase CBX4 (CBX4)

E3 SUMO-protein ligase which eases SUMO1 conjugation by UBE2I (PubMed:12679040). Involved in the sumoylation of HNRNPK, a p53/TP53 transcriptional coactivator, hence indirectly regulates p53/TP53 transcriptional activation leading to p21/CDKN1A expression.

Monosumoylates ZNF131 (PubMed:22825850). .