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Hot-spot p53 mutants interact specifically with two cellular proteins during progression of the cell cycle
1Center for Molecular Medicine, University of Texas Health Science Center at San Antonio 78245.
Abstract:
Inactivation of both alleles of the p53 gene is commonly found in human cancers. In contrast to mutations of the retinoblastoma gene, certain altered forms of p53 gain growth-promoting functions. To explore the mechanisms underlying this gain of function, we have identified two nuclear proteins, with molecular masses of 42 and 38 kDa, respectively, that are specifically associated with p53 mutated within the simian virus 40 T-antigen-binding domain, "hot spots" found in many human tumors. These mutants transactivate the multiple-drug resistance gene promoter and cause cells to grow to higher density. Both the mutated p53 complex with p42 and p38 increase when cells enter S phase of the cell cycle but decrease in G1 and M phases, suggesting that they may have a role in promoting cell growth.
Insights
Certain mutated forms of the p53 gene gain growth-promoting functions in cancer. These mutants associate with nuclear proteins p42 and p38, driving cell proliferation.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Inactivation of both p53 gene alleles is frequent in human cancers.
- Unlike retinoblastoma gene mutations, some altered p53 forms exhibit gain-of-function properties.
- Understanding these gain-of-function mechanisms is crucial for cancer research.
Purpose of the Study:
- To investigate the mechanisms behind p53's gain of function in cancer.
- To identify proteins interacting with mutated p53 within critical functional domains.
Main Methods:
- Proteomic analysis to identify nuclear proteins associated with mutated p53.
- Assessment of p53-protein complex formation and its correlation with cell cycle phases.
- Transactivation assays to evaluate the effect of mutated p53 on gene expression.
Main Results:
- Two nuclear proteins, p42 and p38, were identified as specifically associated with p53 mutated in the simian virus 40 T-antigen-binding domain.
- Mutated p53, complexed with p42 and p38, transactivates the multiple-drug resistance gene promoter.
- These complexes promote increased cell density and are upregulated during the S phase of the cell cycle.
Conclusions:
- Mutated p53, in complex with p42 and p38, exhibits gain-of-function properties.
- The p53-p42/p38 complexes appear to play a role in promoting cancer cell growth, particularly during the S phase.