Related Experiment Videos
Physical and functional interaction between wild-type p53 and mdm2 proteins
D S Haines1, J E Landers, L J Engle
1Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia 19104.
Abstract:
The mdm2 oncogene, which is often amplified in mammalian tumors, produces a number of transcripts that encode distinct protein forms. Previous studies demonstrating that overexpression of the mdm2 gene can activate its transforming potential, and can inhibit the transcriptional activation function of p53, prompted us to begin to explore possible functional differences among the various mdm2 products. Utilizing a transient transfection assay, we have evaluated four naturally occurring murine mdm2 forms for their ability to inhibit p53-mediated transcriptional activation of reporter genes regulated by p53 response elements. Three of these mdm2 forms were found to physically associate with the wild-type p53 protein and to possess the ability to inhibit its transactivation function. A fourth form failed to exhibit either of these functions. This last mdm2 form lacks the N-terminal protein domain that is present in the other three splice forms examined, pointing to this region as one that is critical for complex formation with the p53 protein. Identifying such differences among mdm2 proteins provides important clues for dissecting their functional domains, and emphasizes that defining the individual properties of these products will be critical in elucidating the overall growth control function of the mdm2 gene.
Insights
The mdm2 oncogene produces multiple protein forms. Three forms inhibit p53 activity by binding to it, while a fourth lacks this ability, highlighting the importance of the N-terminal domain for mdm2-p53 interaction.
Area of Science:
- Molecular Biology
- Oncology
- Gene Regulation
Background:
- The mdm2 oncogene is amplified in mammalian tumors.
- mdm2 overexpression can activate transforming potential and inhibit p53.
- Multiple mdm2 transcripts encode distinct protein forms with potentially different functions.
Purpose of the Study:
- To investigate functional differences among naturally occurring murine mdm2 protein forms.
- To determine the ability of different mdm2 forms to inhibit p53-mediated transcriptional activation.
Main Methods:
- Transient transfection assays were used.
- Four naturally occurring murine mdm2 forms were evaluated.
- Reporter genes regulated by p53 response elements were utilized.
Main Results:
- Three of the four mdm2 forms physically associated with wild-type p53.
- These three mdm2 forms inhibited p53's transactivation function.
- A fourth mdm2 form, lacking the N-terminal domain, did not associate with p53 or inhibit its function.
Conclusions:
- The N-terminal domain of mdm2 is critical for p53 protein complex formation.
- Functional differences exist among mdm2 protein products.
- Understanding individual mdm2 protein properties is crucial for elucidating mdm2 gene function in growth control.