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Reciprocal interference between the sequence-specific core and nonspecific C-terminal DNA binding domains of p53:
M E Anderson1, B Woelker, M Reed
1Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook 11794-5222, USA.
Abstract:
The tumor suppressor p53 has two DNA binding domains: a central sequence-specific domain and a C-terminal sequence-independent domain. Here, we show that binding of large but not small DNAs by the C terminus of p53 negatively regulates sequence-specific DNA binding by the central domain. Four previously described mechanisms for activation of specific DNA binding operate by blocking negative regulation. Deletion of the C terminus of p53 activates specific DNA binding only in the presence of large DNA. Three activator molecules (a small nucleic acid, a monoclonal antibody against the p53 C terminus, and a C-terminal peptide of p53) stimulate sequence-specific DNA binding only in the presence of both large DNA and p53 with an intact C terminus. Our findings argue that interactions of the C terminus of p53 with genomic DNA in vivo would prevent p53 binding to specific promoters and that cellular mechanisms to block C-terminal DNA binding would be required.
Insights
The C-terminal domain of tumor suppressor p53 inhibits its sequence-specific DNA binding. Activators function by blocking this negative regulation, suggesting in vivo mechanisms are needed to release p53 for promoter binding.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The tumor suppressor p53 protein plays a critical role in cellular responses to DNA damage.
- p53 possesses two distinct DNA binding domains: a central sequence-specific domain and a C-terminal sequence-independent domain.
Purpose of the Study:
- To investigate the regulatory role of the p53 C-terminal domain in sequence-specific DNA binding.
- To elucidate the mechanisms by which p53's DNA binding activity is modulated.
Main Methods:
- Studied the effect of large and small DNA binding on p53's central domain activity.
- Assessed the impact of C-terminal deletion and various activator molecules on p53 DNA binding.
- Investigated the interplay between p53 domains and DNA in vitro.
Main Results:
- Binding of large DNA to the p53 C terminus negatively regulates sequence-specific DNA binding by the central domain.
- Deletion of the C terminus enhances sequence-specific binding, particularly with large DNA.
- Activator molecules (nucleic acid, antibody, peptide) promote p53 binding by overcoming C-terminal inhibition.
Conclusions:
- The p53 C terminus acts as a negative regulator of sequence-specific DNA binding through interaction with large DNA.
- Cellular mechanisms likely exist to counteract this C-terminal inhibition, enabling p53 to bind specific gene promoters in vivo.