Enables several functions, including SUMO binding activity; SUMO transferase activity; and nucleic acid binding activity. Acts upstream of or within negative regulation of transcription by RNA polymerase II and protein sumoylation. Located in nuclear body. Is expressed in several structures, including adrenal gland; brain; gut; lung; and thymus. Human ortholog(s) of this gene implicated in hepatocellular carcinoma. Orthologous to human CBX4 (chromobox 4). [provided by Alliance of Genome Resources, Apr 2022]