MDM4 is a nuclear protein that contains a p53 binding domain at the N-terminus and a RING finger domain at the C-terminus. MDM4 shows structural similarity to p53-binding protein MDM2 and both proteins bind the p53 tumor suppressor protein and inhibit its activity. However, unlike MDM2, MDM4 does not cause nuclear export or degradation of p53. Instead, MDM4 inhibits p53 activity by binding to the transcriptional activation domain of p53. MDM4 is overexpressed in a variety of human cancers (1). Expression level of MDM4 is significantly higher in chronic lymphocytic leukemia. MDM4 is a specific chemotherapeutic target for treating retinoblastoma (2). MDM4 Protein is ideal for investigators involved in Signaling Proteins, Cell Cycle Proteins, AKT/PKB Pathway, Apoptosis/Autophagy, Cancer, Cell Cycle, and Cellular Stress research.