Mouse double minute 2 homolog and Mouse double minute X homolog (MDM2 and MDMX (also known as MDM4))

Mouse double minute 2 homolog (MDM2) and mouse double minute X homolog (MDMX, also known as MDM4) are closely related oncoproteins that function as major negative regulators of the tumor suppressor p53[2][3][4][5]. MDM2 acts as an E3 ubiquitin ligase, targeting p53 for proteasomal degradation, thereby maintaining low p53 levels under normal physiological conditions; it can also autoubiquitinate and target MDMX for degradation[3][5][6]. MDMX lacks intrinsic ubiquitin ligase activity but binds p53 and modulates MDM2 function—together, they can form RING domain heterodimers essential for effective p53 suppression[3][5]. Both proteins are essential for embryonic development, and their overexpression or gene amplification is implicated in diverse human cancers, often resulting in loss of p53 tumor suppressor activity. MDM2 and MDMX represent canonical cancer therapy targets; small molecule inhibitors that disrupt the p53-MDM2/MDMX interaction are being clinically developed as precision cancer treatments in tumors retaining wild-type p53[2][4][5].

Other names

Proto-oncogene protein c-mdm2E3 ubiquitin-protein ligase Mdm2HDM2 (human)Proto-oncogene protein c-mdmxMDM4HDMX

Inhibitors restore p53 function by blocking the MDM2-p53 or MDMX-p53 interaction, leading to p53 activation, induction of cell cycle arrest and/or apoptosis in tumor cells with wild-type p53[4] Some agents inhibit ubiquitin ligase activity directly