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p53: a transdominant regulator of transcription whose function is ablated by mutations occurring in human cancer
1National Cancer Institute, NCI-Navy Medical Oncology Branch, Bethesda, MD.
Abstract:
Gal4-p53 fusion constructs demonstrate that wild type p53 is a potent transactivator in human lung cancer cells with the transactivation domain for p53 residing in amino acids 1-42. Strikingly, a variety of lung cancer derived p53 mutations occurring outside this domain disrupt this activity. Temperature sensitive conformational shifts of p53 mutant proteins to the wild type form exist and, with a temperature downshift, several mutants become transcriptionally active. Wild type p53 protein is known to form oligomers with mutant p53 and cotransfection of wild type and mutant genes shows that p53 acts in a transdominant manner that is independent of the DNA binding specificity. Transcription is either increased or decreased depending on whether the wild type is more or less abundant than the mutant form. Finally, lung cancers differ in their ability to support the transactivation related functions, providing evidence of other abnormalities of the p53 system in human cancer.
Insights
Wild type p53 protein is a potent transactivator in lung cancer cells. Mutations outside its transactivation domain disrupt this, but some mutants regain activity upon temperature shift, revealing insights into p53
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- The tumor suppressor protein p53 is frequently mutated in human cancers, including lung cancer.
- Understanding the transactivation function of wild-type and mutant p53 is crucial for cancer therapy.
Purpose of the Study:
- To investigate the transactivation potential of wild-type and mutant p53 in human lung cancer cells.
- To identify the transactivation domain of p53 and analyze the impact of mutations on its function.
- To explore the oligomerization and dominant-negative effects of p53 mutants.
Main Methods:
- Utilized Gal4-p53 fusion constructs to assess transactivation activity.
- Introduced various lung cancer-derived p53 mutations into the fusion constructs.
- Performed temperature shift experiments to evaluate temperature-sensitive mutants.
- Co-transfected wild-type and mutant p53 genes to study oligomerization and transdominance.
Main Results:
- Wild-type p53 functions as a potent transactivator in lung cancer cells, with the transactivation domain located in amino acids 1-42.
- Mutations outside this domain disrupt transactivation, but temperature-sensitive mutants can regain activity upon a temperature downshift.
- p53 exhibits transdominant behavior, forming oligomers with mutant p53 in a manner independent of DNA binding specificity.
- The relative abundance of wild-type and mutant p53 influences transcriptional activity, either increasing or decreasing it.
- Lung cancers exhibit differential abilities to support p53 transactivation functions, suggesting additional abnormalities in the p53 pathway.
Conclusions:
- The N-terminal region (amino acids 1-42) of p53 is critical for its transactivation function in lung cancer.
- Temperature-sensitive p53 mutants offer potential therapeutic targets by restoring wild-type function.
- p53's transdominant activity and oligomerization with mutants contribute to its tumor suppressor role and oncogenic செயல்பாடுகள்.
- Heterogeneity in lung cancers reflects diverse alterations within the p53 system, impacting therapeutic strategies.