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Structural state of newly replicated closed circular simian virus 40 DNA
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Journal of Virology
|October 1, 1988
Summary
Newly replicated simian virus 40 (SV40) DNA transitions into a mature supercoiled state. Research shows newly synthesized SV40 DNA molecules are initially more relaxed than mature DNA.
Area of Science:
- Molecular Biology
- Virology
Background:
- Simian virus 40 (SV40) is a widely used model system for studying DNA replication and viral assembly.
- Understanding the structural transitions of viral DNA post-replication is crucial for comprehending the viral life cycle.
Purpose of the Study:
- To investigate the early structural state of newly replicated simian virus 40 (SV40) DNA molecules.
- To determine the transition process of nascent SV40 DNA into its mature, supercoiled form.
Main Methods:
- SV40-infected African green monkey kidney CV1 cells were labeled with radioactive thymidine isotopes ([14C] and [3H]).
- Viral DNA was isolated and analyzed using cesium chloride density gradient centrifugation.
- DNA structural states were further assessed via agarose gel electrophoresis in the presence of chloroquine.
Main Results:
- Newly synthesized SV40 DNA molecules exhibited a slightly higher buoyant density compared to chronically labeled DNA.
- Electrophoretic mobility analysis indicated that nascent SV40 DNA was in a more relaxed structural state.
- The observed differences suggest newly completed SV40 DNA molecules were less supercoiled by one to two linking numbers.
Conclusions:
- Newly replicated SV40 DNA molecules undergo a transition from a relaxed state to a mature, fully supercoiled form.
- This structural maturation is a critical step in the viral DNA lifecycle following replication.
- The findings provide insights into the dynamic structural changes of viral DNA within host cells.