DNA synthesis by RNA-containing tumor viruses

Area of Science:

• Virology
• Molecular Biology
• Oncology

Background:

• Murine leukemia (Rauscher and Moloney strains) and sarcoma (Kirsten strain) virions, along with the mouse mammary tumor virus, are RNA viruses.
• These viruses are associated with oncogenic properties.

Purpose of the Study:

• To investigate the presence and properties of RNA-dependent DNA polymerase in oncogenic murine viruses.
• To determine the optimal conditions for the enzymatic activity of this polymerase.

Main Methods:

• Enzyme assays were performed on purified virions.
• The effect of Triton X-100 detergent concentration on enzyme activity was evaluated.
• Sucrose gradient centrifugation was used to analyze the sedimentation of virions, enzyme activity, and newly synthesized DNA.

Main Results:

• RNA-dependent DNA polymerase activity was detected in Rauscher and Moloney leukemia viruses, Kirsten sarcoma virus, and mouse mammary tumor virus.
• Optimal enzyme activity occurred at a specific Triton X-100 concentration (0.010-0.014%).
• Higher detergent concentrations disrupted the virions and abolished enzyme activity. The enzyme, virion, and synthesized DNA cosedimented, indicating association.

Conclusions:

• Oncogenic RNA viruses possess RNA-dependent DNA polymerase activity.
• This enzymatic activity is sensitive to detergent concentration, requiring specific conditions for optimal function.
• The presence of this enzyme is currently linked exclusively to oncogenic RNA viruses.