HIV-1 Accessory Protein Vpr Interacts with REAF/RPRD2 To Mitigate Its Antiviral Activity

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• The human immunodeficiency virus type 1 (HIV-1) accessory protein Vpr is essential for efficient viral replication in macrophages.
• Vpr is packaged within the virion and functions early in the infection cycle.
• REAF (RNA-associated early-stage antiviral factor; RPRD2) is a known inhibitor of HIV replication during reverse transcription.

Purpose of the Study:

• To investigate the mechanism by which HIV-1 Vpr enhances viral replication in macrophages.
• To determine the role of REAF in HIV-1 infection and its interaction with Vpr.
• To elucidate the molecular basis of Vpr-mediated suppression of REAF's antiviral activity.

Main Methods:

• Virus-like particle (VLP) delivery to introduce Vpr into primary macrophages.
• Coimmunoprecipitation assays to detect protein interactions.
• Analysis of REAF degradation kinetics and Vpr mutant effects on degradation.
• Assessment of REAF expression levels in response to infection.

Main Results:

• HIV-1 Vpr directly induces the degradation of REAF in primary macrophages.
• REAF degradation by Vpr occurs rapidly, within 30 minutes of viral entry.
• Vpr-mediated REAF degradation requires Vpr's nuclear localization and interaction with the CUL4A-DBB1(DCAF1) E3 ubiquitin ligase complex.
• Vpr counteracts the upregulation of REAF levels that normally occurs in response to HIV infection.

Conclusions:

• HIV-1 Vpr degrades the antiviral factor REAF, thereby promoting viral replication in macrophages.
• Vpr's interaction with the host cell's protein degradation machinery is critical for overcoming REAF-mediated restriction.
• These findings explain a key mechanism by which Vpr facilitates HIV-1 infection of macrophages.