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Sequence-specific interaction of a conformational domain of p53 with DNA
R Srinivasan1, J A Roth, S A Maxwell
1Department of Thoracic and Cardiovascular Surgery, University of Texas M. D. Anderson Cancer Center, Houston 77030.
Abstract:
Mutations within a conserved "conformational" domain of the p53 protein have frequently been observed in a wide variety of human cancers. A hybrid protein containing the wild-type conformational domain of p53 fused to protein A bound to calf thymus DNA and a specific p53 DNA-binding motif. Hybrid proteins containing mutations in p53 bound to DNA less efficiently than wild-type hybrid protein. In addition, competition experiments showed that mutated p53 DNA-binding motif failed to interact with p53 hybrid proteins. The DNA-binding activity of wild-type p53 hybrid protein was inhibited by the metal chelator 1,10-phenanthroline. These results demonstrate that DNA-binding activity resides in the conformational domain of p53, providing a structural model for disruption of DNA binding by mutation. Furthermore, metal ions may regulate binding of p53 to DNA by modulating its conformation.
Insights
Mutations in the p53 protein
Area of Science:
- Molecular Biology
- Cancer Research
- Protein Biochemistry
Background:
- Mutations in the p53 protein's conformational domain are common in human cancers.
- Understanding p53's DNA-binding mechanism is crucial for cancer therapy.
Purpose of the Study:
- To investigate the role of the p53 conformational domain in DNA binding.
- To elucidate the structural basis of p53 mutations affecting DNA binding.
- To explore the influence of metal ions on p53 DNA-binding activity.
Main Methods:
- Constructed hybrid proteins: wild-type p53 conformational domain fused to protein A, with a p53 DNA-binding motif.
- Assessed DNA-binding efficiency of wild-type versus mutated hybrid proteins.
- Performed competition assays to evaluate interactions between mutated motifs and hybrid proteins.
- Utilized the metal chelator 1,10-phenanthroline to inhibit DNA-binding activity.
Main Results:
- Mutated p53 hybrid proteins exhibited reduced DNA-binding efficiency compared to wild-type.
- Mutated p53 DNA-binding motifs did not interact with p53 hybrid proteins in competition assays.
- 1,10-phenanthroline inhibited the DNA-binding activity of wild-type p53 hybrid protein.
- DNA-binding activity was localized to the p53 conformational domain.
Conclusions:
- The conformational domain of p53 is essential for its DNA-binding activity.
- Mutations in this domain disrupt DNA binding, offering a structural model for cancer-related alterations.
- Metal ions may play a regulatory role in p53's DNA binding by influencing protein conformation.