May play a role in MDM2-dependent p53/TP53 homeostasis in unstressed cells. Inhibits autoubiquitination of MDM2, thereby enhancing MDM2 stability. This promotes MDM2-mediated ubiquitination of p53/TP53 and its subsequent degradation. Inhibits cell migration in vitro and suppresses the invasive behavior of tumor cells. Interacts with MDM2. Expressed in small intestine and spleen at low levels, in the ovary at intermediate levels and in the testis and thymus at high levels. Death between E3.5 and E7.5. Mice containing a heterozygous deletion of this gene coupled with heterozygous deletion of TP53 exhibit an increased incidence of metastatic tumors. Belongs to the MTBP family.