Related Experiment Videos
Oncoprotein MDM2 conceals the activation domain of tumour suppressor p53
J D Oliner1, J A Pietenpol, S Thiagalingam
1Johns Hopkins Oncology Centre, Baltimore, Maryland 21231.
Abstract:
The tumour-suppressor gene p53 is inactivated in most human malignancies either by missense mutations or by binding to oncogenic proteins. In human soft tissue sarcomas, inactivation apparently results from MDM2 gene amplification. MDM2 is an oncogene product that may function by binding to p53 and inhibiting its ability to activate transcription. Here we show that, when expressed in Saccharomyces cerevisiae, human MDM2 inhibits human p53's ability to stimulate transcription by binding to a region that nearly coincides with the p53 acidic activation domain. The isolated p53 activation domain fused to another DNA-binding protein is also inactivated by MDM2, confirming that MDM2 can inhibit p53 function by concealing the activation domain of p53 from the cellular transcription machinery.
Insights
The tumor suppressor p53 is often inactivated in cancers. The MDM2 oncogene inhibits p53 function by binding to its activation domain, preventing transcription.
Area of Science:
- Molecular Biology
- Cancer Biology
- Biochemistry
Background:
- The tumor suppressor p53 is crucial for preventing cancer and is frequently inactivated in human malignancies.
- Inactivation of p53 can occur through mutations or binding to oncogenic proteins, such as MDM2.
- MDM2 amplification is implicated in the inactivation of p53 in human soft tissue sarcomas.
Purpose of the Study:
- To investigate the mechanism by which the MDM2 oncogene product inhibits the function of the tumor suppressor p53.
- To determine if MDM2 directly interferes with p53's transcriptional activation capabilities.
Main Methods:
- Expression of human p53 and MDM2 in Saccharomyces cerevisiae (yeast).
- Assays to measure the transcriptional activity of p53.
- Analysis of p53-MDM2 interaction using a DNA-binding protein fused to the p53 activation domain.
Main Results:
- Human MDM2 significantly inhibits the transcriptional activity of human p53 when co-expressed in yeast.
- MDM2 binds to a region of p53 that overlaps with its acidic activation domain.
- MDM2 also inactivates a DNA-binding protein fused to the p53 activation domain, indicating direct interference with the activation domain.
Conclusions:
- MDM2 inhibits p53's tumor-suppressive function by directly binding to and concealing its transcriptional activation domain.
- This interaction prevents p53 from effectively stimulating gene transcription, contributing to oncogenesis.
- The findings elucidate a key mechanism of p53 inactivation by MDM2, relevant to cancer development.