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Identification of p53 as a sequence-specific DNA-binding protein
S E Kern1, K W Kinzler, A Bruskin
1Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
Science (New York, N.Y.)
|June 21, 1991
Summary
The tumor-suppressor protein p53, crucial in preventing cancer, binds to specific DNA sequences. Mutations common in human tumors disrupt this DNA binding ability, impairing its function.
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- The tumor-suppressor gene p53 plays a critical role in human malignancies.
- The biochemical functions of p53 and the impact of mutations remain incompletely understood.
Purpose of the Study:
- To investigate the DNA-binding properties of wild-type p53.
- To determine the effect of common tumor-associated mutations on p53 DNA binding.
Main Methods:
- Identification and characterization of a specific human DNA binding sequence for wild-type p53.
- In vitro binding assays using purified p53 proteins and DNA fragments.
- Site-directed mutagenesis and chemical modification (methylation) of the DNA sequence to assess critical binding sites.
Main Results:
- A specific 33-base pair human DNA sequence was identified that binds selectively to wild-type p53 protein.
- Specific guanine residues within this sequence were essential for p53 binding; methylation or substitution abrogated binding.
- Human p53 proteins with common tumor-associated missense mutations showed significantly reduced or abolished binding to the identified DNA sequence.
Conclusions:
- Wild-type p53 protein possesses the ability to bind to specific DNA sequences in the human genome.
- This DNA-binding activity is a likely functional mechanism of p53's tumor-suppressive role.
- Common missense mutations found in human tumors alter and likely inactivate the DNA-binding function of p53.