Human immunodeficiency virus reverse transcriptase displays a partially processive 3' to 5' endonuclease activity.

Area of Science:

• Biochemistry
• Molecular Biology
• Virology

Background:

• Human immunodeficiency virus reverse transcriptase (HIV-RT) is crucial for viral replication.
• The ribonuclease H (RNase H) domain of HIV-RT plays a role in RNA degradation during reverse transcription.
• Understanding the RNase H activity is essential for developing antiviral therapies.

Purpose of the Study:

• To characterize the ribonuclease H (RNase H) activity of human immunodeficiency virus reverse transcriptase (HIV-RT).
• To determine the enzymatic properties, including directionality and processivity, of the RNase H domain.
• To investigate the influence of ionic strength on HIV-RT's RNase H activity.

Main Methods:

• Utilized an 83-nucleotide RNA template hybridized to a DNA oligomer as a substrate.
• Employed electrophoretic methods to resolve RNase H cleavage products.
• Performed assays with excess competitor RNA to analyze single enzyme binding events.

Main Results:

• HIV-RT's RNase H activity is highly sensitive to ionic strength, with optimal activity at low KCl concentrations.
• Enzyme-substrate binding stability increased significantly with decreasing KCl concentration.
• Cleavage products indicated an endonucleolytic activity directed from 3' to 5', with limited processivity.

Conclusions:

• HIV-RT possesses a partially processive endonuclease activity within its RNase H domain.
• The enzyme's activity is modulated by ionic strength, affecting its binding and cleavage kinetics.
• These findings provide insights into the mechanism of reverse transcription and potential therapeutic targets.