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Allosteric control of simian virus 40 T-antigen binding to viral origin DNA
Abstract:
Simian virus 40 (SV40) large tumor antigen (T antigen) possesses several biochemical activities localized in different domains of the protein. These activities include sequence-specific binding to two major sites, I and II, in the SV40 control region, ATPase, and nucleotide-binding activity. In the present communication, we present evidence that specific binding of immunopurified T antigen to SV40 DNA is markedly inhibited by low concentrations of ATP, dATP, GTP, and dGTP. The inhibition is reversible after removal of the nucleotide, suggesting that simple nucleotide binding rather than a covalent modification of T antigen in the presence of ATP is responsible for the inhibition. The results suggest that T antigen may assume two conformations, one active and one inactive in binding to the SV40 origin of replication. In the presence of purine nucleoside triphosphates, the inactive conformation is favored.
Insights
Simian virus 40 (SV40) large tumor antigen (T antigen) binding to SV40 DNA is inhibited by purine nucleoside triphosphates. This suggests T antigen may switch between active and inactive conformations for DNA replication.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Simian virus 40 (SV40) large tumor antigen (T antigen) exhibits multiple biochemical activities.
- These include sequence-specific DNA binding, ATPase, and nucleotide binding.
Purpose of the Study:
- To investigate the effect of nucleotides on T antigen's binding to SV40 DNA.
- To understand the mechanism regulating T antigen's DNA binding activity.
Main Methods:
- Immunopurification of T antigen.
- DNA binding assays using SV40 DNA.
- Assessment of nucleotide influence on T antigen-DNA interaction.
Main Results:
- Low concentrations of ATP, dATP, GTP, and dGTP significantly inhibited T antigen's specific binding to SV40 DNA.
- The inhibition was reversible upon nucleotide removal, indicating non-covalent interaction.
- Purine nucleoside triphosphates favor an inactive DNA-binding conformation of T antigen.
Conclusions:
- T antigen's DNA binding is regulated by purine nucleoside triphosphates.
- SV40 T antigen likely exists in at least two conformations: active and inactive for DNA binding.
- Nucleotide binding induces a conformational change, potentially modulating viral DNA replication initiation.