Major mediator of the tumor suppressor activity of IFN in breast cancer cells. Promotes ubiquitination and subsequent degradation of MDM2, which leads to p53/TP53 stabilization. Promotes ubiquitination and subsequent degradation of HDAC1, which in turn enhances maspin expression, and impairs invasive activity of cancer cells. Interacts with MDM2. Expressed in spleen, lymph node and peripheral blood leukocytes, and at lower levels in thymus, bone marrow and fetal liver. Down-regulated in breast tumors. By IFN-alphas and IFNG/IFN-gamma in hematopoietic cancer cells. The HIN-200 domain mediates interaction with MDM2. Belongs to the HIN-200 family.