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Updated: Oct 9, 2026
Yeast As a Chassis for Developing Functional Assays to Study Human P53
Published on: August 4, 2019
A subset of tumor-derived mutant forms of p53 down-regulate p63 and p73 through a direct interaction with the p53
1Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Abstract:
The p53 protein is related by sequence homology and function to the products of two other genes, p63 and p73, that each encode several isoforms. We and others have discovered previously that certain tumor-derived mutants of p53 can associate and inhibit transcriptional activation by the alpha and beta isoforms of p73. In this study we have extended these observations to show that in transfected cells a number of mutant p53 proteins could bind and down-regulate several isoforms not only of p73 (p73 alpha, -beta, -gamma, and -delta) but also of p63 (p63 alpha and -gamma; Delta Np63 alpha and -gamma). Moreover, a correlation existed between the efficiency of p53 binding and the inhibition of p63 or p73 function. We also found that wild-type p63 and p73 interact efficiently with each other when coexpressed in mammalian cells. The interaction between p53 mutants and p63 or p73 was confirmed in a physiological setting by examining tumor cell lines that endogenously express these proteins. We also demonstrated that purified p53 and p73 proteins interact directly and that the p53 core domain, but not the tetramerization domain, mediates this interaction. Using a monoclonal antibody (PAb240) that recognizes an epitope within the core domain of a subset of p53 mutants, we found a correlation between the ability of p53 proteins to be immunoprecipitated by this antibody and their ability to interact with p73 or p63 in vitro and in transfected cells. Based on these results and those of others, we propose that interactions between the members of the p53 family are likely to be widespread and may account in some cases for the ability of tumor-derived p53 mutants to promote tumorigenesis.
Insights
Mutant p53 proteins can inhibit the function of p63 and p73 proteins, which are related to p53. These interactions, confirmed in tumor cells, suggest widespread p53 family interactions contributing to cancer development.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- The p53 protein family, including p53, p63, and p73, plays critical roles in cellular processes.
- Mutations in p53 are common in human cancers.
- Previous studies indicated that some tumor-derived p53 mutants can interfere with p73 function.
Purpose of the Study:
- To investigate the interactions between mutant p53 proteins and various isoforms of p63 and p73.
- To determine if these interactions affect the transcriptional activity of p63 and p73.
- To explore the physiological relevance and molecular basis of these interactions.
Main Methods:
- Transfection of cells with expression vectors for p53 mutants, p63, and p73 isoforms.
- Co-immunoprecipitation assays to detect protein-protein interactions.
- Reporter gene assays to measure transcriptional activation.
- Analysis of endogenous protein interactions in tumor cell lines.
- In vitro binding assays with purified proteins.
- Use of a specific monoclonal antibody (PAb240) targeting a p53 mutant epitope.
Main Results:
- Mutant p53 proteins bind to and down-regulate multiple isoforms of both p63 and p73.
- The efficiency of p53 binding correlates with the degree of inhibition of p63/p73 function.
- Wild-type p63 and p73 interact with each other.
- Interactions between p53 mutants and p63/p73 are observed in endogenous systems (tumor cell lines).
- Direct interaction between purified p53 and p73 is mediated by the p53 core domain.
- Antibody PAb240 recognition of p53 mutants correlates with their ability to interact with p63/p73.
Conclusions:
- Interactions among p53 family members (p53, p63, p73) are extensive.
- Mutant p53 proteins can inhibit the function of p63 and p73.
- These interactions may contribute to tumorigenesis by disrupting normal p53 family functions.
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