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Differential interaction of temperature-sensitive simian virus 40 T antigens with tumor suppressors pRb and p53
S Ray1, M E Anderson, P Tegtmeyer
1Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, New York 11794-5222, USA.
Abstract:
Previous studies have shown that simian virus 40 large T antigen transforms cells by binding and inactivating suppressors of cell cycle progression and tumor formation. Here, we characterize the interactions of five temperature-sensitive T antigens with the tumor suppressor proteins pRb and p53. All five mutant T antigens bind pRb at the nonpermissive temperature with efficiencies similar to that of wild-type T antigen. A single transformation-competent mutant, with a substitution of amino acid 186, binds p53 at the nonpermissive temperature. Four transformation-defective mutants, with a substitution at T antigen position 357, 422, 427, or 438, are temperature sensitive for the binding and inactivation of p53. Our findings provide a basis for understanding the behavior of cells transformed by temperature-sensitive T antigens.
Insights
Temperature-sensitive simian virus 40 large T antigens were studied for their interaction with tumor suppressor proteins pRb and p53. Mutants affecting p53 binding correlate with transformation ability and temperature sensitivity.
Area of Science:
- Molecular Biology
- Virology
- Oncology
Background:
- Simian virus 40 (SV40) large T antigen (LT) is a viral oncoprotein.
- LT transforms cells by inactivating tumor suppressor proteins like pRb and p53, which regulate cell cycle progression.
- Understanding LT's interactions is crucial for cancer research.
Purpose of the Study:
- To characterize the binding interactions of five temperature-sensitive SV40 LT mutants.
- To investigate the relationship between LT binding to pRb and p53 and cellular transformation.
- To elucidate the role of specific amino acid substitutions in LT's function.
Main Methods:
- Utilized temperature-sensitive SV40 large T antigen mutants.
- Assessed binding affinities to tumor suppressor proteins pRb and p53 at permissive and non-permissive temperatures.
- Correlated binding characteristics with cellular transformation competence.
Main Results:
- All five temperature-sensitive LT mutants bound pRb similarly to wild-type LT at non-permissive temperatures.
- One transformation-competent mutant showed p53 binding at non-permissive temperatures.
- Four transformation-defective mutants exhibited temperature-sensitive binding and inactivation of p53.
Conclusions:
- Specific interactions with p53, particularly temperature-sensitive binding and inactivation, are critical for SV40-mediated cellular transformation.
- Amino acid substitutions at positions 357, 422, 427, or 438 in LT affect p53 interaction and transformation.
- These findings provide a foundation for understanding the mechanisms of temperature-sensitive viral oncogenesis.