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Yeast As a Chassis for Developing Functional Assays to Study Human P53
Published on: August 4, 2019
The p53 proto-oncogene can act as a suppressor of transformation
C A Finlay1, P W Hinds, A J Levine
1Princeton University, Department of Biology, New Jersey 08540-1014.
Abstract:
DNA clones of the wild-type p53 proto-oncogene inhibit the ability of E1A plus ras or mutant p53 plus ras-activated oncogenes to transform primary rat embryo fibroblasts. The rare clones of transformed foci that result from E1A plus ras plus wild-type p53 triple transfections all contain the p53 DNA in their genome, but the great majority fail to express the p53 protein. The three cell lines derived from such foci that express p53 all produce mutant p53 proteins with properties similar or identical to transformation-activated p53 proteins. The p53 mutants selected in this fashion (transformation in vitro) resemble the p53 mutants selected in tumors (in vivo). These results suggest that the p53 proto-oncogene can act negatively to block transformation.
Insights
Wild-type p53 protein acts as a tumor suppressor, inhibiting cell transformation. Mutant p53 proteins, however, promote transformation, similar to those found in tumors.
Area of Science:
- Oncology
- Molecular Biology
- Cellular Biology
Background:
- The p53 proto-oncogene is a critical regulator of cell growth and a known tumor suppressor.
- Oncogenic mutations in p53 are frequent in human cancers, suggesting a role in tumorigenesis.
- Understanding the precise function of wild-type and mutant p53 in cellular transformation is crucial for cancer research.
Purpose of the Study:
- To investigate the role of wild-type p53 in inhibiting cellular transformation induced by oncogenes.
- To characterize the p53 protein status in cells transformed by combinations of oncogenes.
- To compare p53 mutants selected during in vitro transformation with those found in vivo.
Main Methods:
- Transfection of primary rat embryo fibroblasts with DNA clones encoding wild-type p53, oncogenes (E1A, ras), or mutant p53.
- Selection and analysis of transformed cell foci.
- Genomic integration analysis of p53 DNA.
- Western blot analysis to assess p53 protein expression.
Main Results:
- Wild-type p53 DNA clones inhibited transformation mediated by E1A plus ras or mutant p53 plus ras.
- Transformed foci from triple transfections contained p53 DNA, but most failed to express p53 protein.
- Cell lines expressing p53 from these foci predominantly produced mutant p53 proteins.
- In vitro selected p53 mutants exhibited properties similar to in vivo selected tumor-associated p53 mutants.
Conclusions:
- The wild-type p53 proto-oncogene functions as a negative regulator, actively blocking cellular transformation.
- Selection pressure favors the loss of wild-type p53 function or the acquisition of activating p53 mutations during oncogene-induced transformation.
- p53 mutants selected in vitro share characteristics with those found in naturally occurring tumors, highlighting their oncogenic potential.
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