Protein Mdm4 (MDM4) (MDM4)

Protein Mdm4 (MDM4), also commonly referred to as MDMX, is a vital negative regulator of the p53 tumor suppressor pathway [1]. It possesses an N-terminal domain that binds to the transactivation domain of p53, effectively masking its ability to initiate the transcription of target genes involved in cell cycle arrest and apoptosis [2]. While MDM4 lacks the intrinsic E3 ubiquitin ligase activity found in its homolog MDM2, it forms a stable heterodimer with MDM2 via their respective C-terminal RING domains, which significantly enhances the efficiency of p53 ubiquitination and subsequent proteasomal degradation [3]. MDM4 is frequently overexpressed or amplified in a wide range of human malignancies, such as breast cancer, sarcomas, and acute myeloid leukemia, making it a high-priority target for cancer therapy [1, 2]. Pharmacological interventions, including stapled peptides like ALRN-6924 and small-molecule inhibitors, aim to disrupt the MDM4-p53 interaction or the MDM2-MDM4 complex to reactivate wild-type p53 and induce tumor cell death [4]. However, clinical development faces challenges such as dose-limiting hematological toxicities and the potential for tumors to acquire p53 mutations as a resistance mechanism [2, 4]. Beyond its role in p53 regulation, MDM4 has been implicated in p53-independent functions, including the regulation of p73 and the DNA damage response [1, 3]. Understanding the complex interplay between MDM4, MDM2, and p53 is essential for the successful implementation of targeted therapies in oncology [2]. (Sources: [1] UniProt O15151; [2] NIH PMC4930919; [3] PubMed 32300648; [4] MDPI Molecules 2025, 30(1), 186)

Other names

MDMXHDMXMdm2-like p53-binding proteinp53-binding protein Mdm4Double minute 4 proteinMRP1BMFS6

Inhibition of the protein-protein interaction between MDM4 and p53, or disruption of the MDM2-MDM4 heterodimer complex to prevent p53 degradation and restore its tumor-suppressive activity.