Inhibition of p53 DNA Binding Function by the MDM2 Protein Acidic Domain

• Published in: The Journal of biological chemistry 2011-05, Vol.286 (18), p.16018-16029
• Main Authors: Cross, Brittany, Chen, Lihong, Cheng, Qian, Li, Baozong, Yuan, Zhi-Min, Chen, Jiandong
• Format: Article
• Language: English
• Subjects: Antibodies - chemistry; ARF; Boronic Acids - pharmacology; Bortezomib; Cell Biology; Cell Line; Conformation; DNA - genetics; DNA - metabolism; DNA-Protein Interaction; E3 Ubiquitin Ligase; Epitopes - genetics; Epitopes - metabolism; Humans; MDM2; MDMX; Methyltransferases - genetics; Methyltransferases - metabolism; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; p53; Promoter Regions, Genetic - physiology; Protease Inhibitors - pharmacology; Proteasome; Proteasome Inhibitors; Protein Folding; Protein Structure, Tertiary; Proto-Oncogene Proteins c-mdm2 - antagonists & inhibitors; Proto-Oncogene Proteins c-mdm2 - genetics; Proto-Oncogene Proteins c-mdm2 - metabolism; Pyrazines - pharmacology; Repressor Proteins - genetics; Repressor Proteins - metabolism; Transcription, Genetic - drug effects; Transcription, Genetic - physiology; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism; Ubiquitination - drug effects; Ubiquitination - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.228981

MDM2 regulates p53 predominantly by promoting p53 ubiquitination. However, ubiquitination-independent mechanisms of MDM2 have also been implicated. Here we show that MDM2 inhibits p53 DNA binding activity in vitro and in vivo. MDM2 binding promotes p53 to adopt a mutant-like conformation, losing reactivity to antibody Pab1620, while exposing the Pab240 epitope. The acidic domain of MDM2 is required to induce p53 conformational change and inhibit p53 DNA binding. Alternate reading frame binding to the MDM2 acidic domain restores p53 wild type conformation and rescues DNA binding activity. Furthermore, histone methyl transferase SUV39H1 binding to the MDM2 acidic domain also restores p53 wild type conformation and allows p53-MDM2-SUV39H1 complex to bind DNA. These results provide further evidence for an ubiquitination-independent mechanism of p53 regulation by MDM2 and reveal how MDM2-interacting repressors gain access to p53 target promoters and repress transcription. Furthermore, we show that the MDM2 inhibitor Nutlin cooperates with the proteasome inhibitor Bortezomib by stimulating p53 DNA binding and transcriptional activity, providing a rationale for combination therapy using proteasome and MDM2 inhibitors.