Biological activity of the intact and cleaved DNA of the simian adenovirus 7

Area of Science:

• Molecular Biology
• Virology
• Oncology

Background:

• Simian adenovirus 7 (SA 7) is a virus known to cause tumors.
• The role of viral DNA and associated proteins in oncogenesis is a key area of research.

Purpose of the Study:

• To investigate the transforming and tumorigenic potential of SA 7 DNA and its complex with terminal protein (TP).
• To determine the influence of DNA cleavage by endonucleases on SA 7's oncogenic activity and infectivity.

Main Methods:

• Deproteinization of SA 7 DNA.
• Formation of SA 7 DNA-TP complexes.
• Infectivity assays in monkey kidney cells.
• Tumorigenicity assays in cell cultures.
• Restriction endonuclease digestion of SA 7 DNA.

Main Results:

• Deproteinized SA 7 DNA exhibited transforming and tumorigenic activity.
• SA 7 DNA-TP complex lost transforming and tumorigenic activity but showed 30-50 times higher infectious titers.
• DNA cleavage enhanced tumorigenic potential of pure DNA, reduced infectivity, and did not restore transformation capacity to the DNA-TP complex.
• The oncogene was localized to the left terminal fragment (minimal size 4.3x10^6 D with R.Sal I).
• Tumorigenic activity decreased with increasing size of the oncogene-containing DNA fragment.

Conclusions:

• Terminal protein (TP) inhibits the transforming and tumorigenic activity of simian adenovirus 7 (SA 7) DNA.
• Cleavage of SA 7 DNA by specific endonucleases can modulate its oncogenic potential and infectivity.
• The oncogene responsible for tumorigenicity is located in the left terminal region of the SA 7 genome.