Functional interplay between MDM2, p63/p73 and mutant p53

Area of Science:

• Oncology
• Molecular Biology
• Protein Interactions

Background:

• Mutant p53 proteins often gain oncogenic functions, driving tumor progression.
• Mutant p53 interacts with p53 family members p63 and p73, influencing their activities.
• The role of MDM2 in modulating mutant p53 interactions with p63 and p73 is not fully understood.

Purpose of the Study:

• To investigate the role of MDM2 in the interactions between mutant p53, p63, and p73.
• To determine how MDM2 affects the binding affinities and functional outcomes of these protein complexes.

Main Methods:

• Analysis of p53, p63, p73, and MDM2 protein interactions using various mutant p53 forms (e.g., R175H, R273H).
• Assessment of MDM2's influence on p63 and p73 binding to mutant p53.
• Evaluation of MDM2's impact on the functional consequences of these interactions, including inhibition of p63 and p73 activity.

Main Results:

• MDM2 binding affinities vary: mutant p53 and p73 bind MDM2 well, while p63 binds weakly.
• MDM2 differentially affects mutant p53 interactions: it inhibits p63 binding to p53R175H but enhances p73 binding to p53R273H.
• MDM2 modulates p63 and p73 activity: it relieves p63 inhibition by p53R175H but enhances p73 inhibition by both p53R175H and p53R273H.

Conclusions:

• MDM2 acts as a key regulator in mutant p53-p63/p73 complexes.
• MDM2 can restore p63 activity by competing for p53R175H binding.
• MDM2 enhances p73 inhibition by forming a trimeric complex with p53R273H and p73, suggesting distinct regulatory mechanisms.