Enables MDM2/MDM4 family protein binding activity; p53 binding activity; and ubiquitin protein ligase activity. Involved in several processes, including DNA metabolic process; regulation of cell cycle phase transition; and response to ionizing radiation. Located in nucleoplasm and site of DNA damage. Colocalizes with site of double-strand break. Implicated in Fanconi anemia. [provided by Alliance of Genome Resources, Apr 2022]