The MDM2 oncogene encodes an inhibitor of the p53 tumor suppressor protein that regulates p53 in a negative feedback loop. MDM2 gene amplification and overexpression occur in several types of tumors and are often associated with poor prognosis. An MDM2 antisense phosphorothioate oligodeoxynucleotide has been identified that effectively inhibits MDM2 expression in tumor cells containing MDM2 gen...

Oral cancers of tobacco and betel chewers represents a unique in-vivo model to understand the genotoxic effect of tobacco and betel carcinogens on oncogenes and tumor suppressor genes. Coordinated interactions of p53 and MDM2 play an important role in regulation of critical growth control gene following exposure to DNA damaging agents. The purpose of this study is to determine if the tumor supp...

MDM2 (HDM2) is a ubiquitin ligase that can target the p53 tumor suppressor protein for degradation. The RING domain is essential for the E3 activity of MDM2, and we show here that the extreme C-terminal tail of MDM2 is also critical for efficient E3 activity. Loss of E3 function in MDM2 mutants deleted of the C-terminal tail correlated with a failure of these mutants to oligomerize with MDM2, o...

The stabilization of p53 against Mdm2-mediated degradation is an important event in DNA damage response. Initial models of p53 stabilization focused on posttranslational modification of p53 that would disrupt the p53-Mdm2 interaction. The N-terminal regions of both p53 and Mdm2 are modified in vivo in response to cellular stress, suggesting that modifications to Mdm2 also may affect the p53-Mdm...

MDM2 can bind the N terminus of p53 and promote its ubiquitination and export from the nucleus to the cytoplasm, where p53 can then be degraded by cytoplasmic proteasomes. Several studies have reported that an intact MDM2 binding domain is necessary for p53 to be targeted for ubiquitination, nuclear export, and degradation by MDM2. In the current study, we examined whether the MDM2 binding doma...

We have demonstrated previously that the oncoprotein Mdm2 has a ubiquitin ligase activity for the tumor suppressor p53 protein. In the present study, we characterize this ubiquitin ligase activity of Mdm2. We first demonstrate the ubiquitination of several p53 point mutants and deletion mutants by Mdm2. The point mutants, which cannot bind to Mdm2, are not ubiquitinated by Mdm2. The ubiquitinat...

MDM2 is the predominant negative regulator of p53 that functions to maintain the appropriate level of expression and activity of this central tumor suppressor. Mdm2-a is a commonly identified splice variant of Mdm2; however, its physiological function is unclear. To gain insight into the activity of MDM2-A and its potential impact on p53, an Mdm2-a transgenic mouse model was generated. Mdm2-a t...

Covalent attachment of SUMO-1 to Mdm2 requires the activation of a heterodimeric Aos1-Uba2 enzyme (ubiquitin-activating enzyme (E1)) followed by the conjugation of Sumo-1 to Mdm2 by Ubc9, a protein with a strong sequence similarity to ubiquitin carrier proteins (E2s). Upon Sumo-1 conjugation, Mdm2 is protected from self-ubiquitination and elicits greater ubiquitin-protein isopeptide ligase (E3)...

MDM2 is a RING domain ubiquitin E3 ligase and a major regulator of the p53 tumor suppressor. MDM2 binds to p53, inactivates p53 transcription function, inhibits p53 acetylation, and promotes p53 degradation. Here, we present evidence that MDM2 interacts with the nuclear corepressor KAP1. The binding is mediated by the N-terminal coiled-coil domain of KAP1 and the central acidic domain of MDM2. ...

The oncoprotein Mdm2 is a RING domain-containing E3 ubiquitin ligase that ubiquitinates G protein-coupled receptor kinase 2 (GRK2) and β-arrestin2, thereby regulating β-adrenergic receptor (βAR) signaling and endocytosis. Previous studies showed that cardiac Mdm2 expression is critical for controlling p53-dependent apoptosis during early embryonic development, but the role of Mdm2 in the develo...