Enables SUMO transferase activity; protein C-terminus binding activity; and protein domain specific binding activity. Involved in several processes, including G1/S transition of mitotic cell cycle; positive regulation of nitrogen compound metabolic process; and visual learning. Located in nucleus. Biomarker of focal segmental glomerulosclerosis. Orthologous to human PIAS1 (protein inhibitor of activated STAT 1). [provided by Alliance of Genome Resources, Apr 2022]