MDM4 (MDM4 Regulator Of P53, also known as MDMX) is a Protein Coding gene. This gene encodes a nuclear protein that contains a p53 binding domain at the N-terminus and a RING finger domain at the C-terminus and shows structural similarity to p53-binding protein MDM2. MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. MDM4, an essential negative regulator of the P53 tumor suppressor, is frequently overexpressed in cancer cells that harbor a wild-type P53. MDM4 is a key regulator of p53, whose biological activities depend on both transcriptional activity and transcription-independent mitochondrial functions. MDM4 binds to p53 and blocks its transcriptional activity.