Monomer and multimer covalently closed circular forms of Rous sarcoma virus DNA

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Viral DNA replication generates covalently closed circular DNA molecules.
• These molecules are typically monomers but can form oligomers.

Purpose of the Study:

• To characterize the sedimentation properties and infectivity of viral DNA oligomers.
• To investigate the stability of infectious circular DNA molecules under different gradient conditions.

Main Methods:

• Neutral and alkaline sucrose gradient sedimentation.
• DNA-RNA hybridization (annealing with complementary DNA).
• Transfection assays to determine infectivity.

Main Results:

• Viral DNA monomers sediment at 22-27S (neutral) and 64-71S (alkaline).
• Infectious circular dimers (peak at 32S) and higher oligomers (3-65S) are detected in neutral gradients.
• Alkali treatment significantly reduces monomer infectivity, obscuring oligomers in alkaline gradients.

Conclusions:

• Viral DNA synthesis produces a population of infectious circular monomers and oligomers.
• Oligomeric forms are less stable or detectable under alkaline conditions due to reduced infectivity.
• Hybridization techniques can detect oligomeric forms after resedimentation.