Differences between the endogenous and exogenous DNA sequences of Rous-associated virus-O

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Endogenous retroviruses, like Rous-associated virus-O (RAV-O), are integrated into host genomes.
• Understanding the integration and sequence characteristics of exogenous retroviruses is crucial for studying viral evolution and pathogenesis.

Purpose of the Study:

• To investigate the DNA sequence characteristics of endogenous and exogenous Rous-associated virus-O (RAV-O) in chicken cell DNA.
• To determine the integration mechanism and potential alterations in exogenous RAV-O proviral DNA.

Main Methods:

• Site-specific DNA endonuclease analysis of cellular DNA from two inbred chicken lines (line 15 and line 100).
• Digestion of cellular DNA and an unintegrated linear RAV-O DNA molecule with various restriction enzymes (Eco RI, Hind III, BgI II, Bam HI, Xho I, Hinc II, Hha I).
• Comparison of DNA fragment patterns from endogenous, exogenous, and mixed RAV-O sequences.

Main Results:

• Endonuclease digestion patterns were identical for endogenous and exogenous RAV-O sequences with most enzymes, but differed with Hinc II and Hha I.
• Specific DNA fragments generated by Hinc II and Hha I from exogenous RAV-O matched those from an unintegrated linear RAV-O DNA molecule, suggesting no cellular DNA contribution.
• Exogenous viral sequences were identical between the two chicken lines, while endogenous sequences showed minor differences.

Conclusions:

• Exogenous proviral sequences integrate into chicken DNA via a virus-specific, cell-nonspecific interaction.
• The free linear DNA intermediate and newly integrated exogenous provirus possess unique endonuclease sites absent in endogenous RAV-O DNA.
• Formation of exogenous RAV-O provirus likely involves specific alterations to endogenous viral DNA sequences prior to reinsertion.