Alterations of the Mdm2 C-Terminus Differentially Impact Its Function In Vivo

Area of Science:

• Molecular Biology
• Genetics
• Cancer Biology

Background:

• Murine double minute 2 (Mdm2) is the primary E3-ubiquitin ligase for the tumor suppressor p53.
• The Mdm2 C-terminal tail is evolutionarily conserved and critical for its function.
• Recent findings linked Mdm2 length mutations to altered p53 response and premature aging.

Purpose of the Study:

• To investigate the in vivo importance of Mdm2 C-terminal tail length on p53 regulatory function.
• To understand the physiological consequences of Mdm2 C-terminus alterations.

Main Methods:

• Engineered three novel mouse alleles using CRISPR-Cas9 technology to modify Mdm2 C-terminal length.
• Conducted genetic studies with these murine models.
• Analyzed mouse embryonic fibroblasts and tissues for p53 activity and gene expression.

Main Results:

• Curtailing Mdm2 C-terminal length by one amino acid caused p53-dependent embryonic lethality.
• Extending Mdm2 C-terminus by five amino acids resulted in smaller mice with fertility issues and shorter lifespans.
• Impaired Mdm2 function correlated with enhanced p53 activity under stress, altered p53 target gene expression, and increased radiosensitivity.

Conclusions:

• The Mdm2 C-terminus length is physiologically critical for regulating p53 functions.
• Even minor alterations to the Mdm2 C-terminus significantly perturb p53 regulation.
• This study confirms the essential role of the conserved Mdm2 C-terminus in maintaining cellular and organismal homeostasis.