Requirements for DNA unpairing during displacement synthesis by HIV-1 reverse transcriptase

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Retroviral replication necessitates DNA displacement synthesis by reverse transcriptase for integration.
• Understanding the mechanism of DNA unwinding by reverse transcriptase is key to inhibiting viral replication.

Purpose of the Study:

• To investigate the DNA melting activity of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase.
• To determine the role of DNA melting in displacement synthesis and identify enzyme regions involved.

Main Methods:

• Utilized potassium permanganate (KMnO(4)) oxidation to detect unpaired thymines in DNA constructs.
• Employed oligonucleotide-based displacement constructs to model reverse transcriptase activity.
• Assessed the impact of nucleotide binding and enzyme mutations on DNA melting.

Main Results:

• DNA melting by HIV-1 reverse transcriptase occurs only after ternary complex formation with the primer and correct deoxynucleoside triphosphate (dNTP).
• Melting is localized to the two base pairs downstream of the primer terminus (+1 and +2 positions).
• A partially impaired mutant (F61W) showed reduced DNA melting, highlighting its importance for displacement synthesis.

Conclusions:

• DNA melting is an essential step mediated by the fingers region of HIV-1 reverse transcriptase in its closed clamp conformation.
• The unpairing reaction is tightly regulated by nucleotide incorporation and enzyme-DNA interaction.
• These findings provide insights into the mechanism of retroviral DNA synthesis and potential therapeutic targets.