Analysis of HIV-1 Matrix-Envelope Cytoplasmic Tail Interactions

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• HIV-1 precursor Gag (PrGag) proteins target viral assembly to the plasma membrane.
• The matrix (MA) domain of PrGag binds phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] at the plasma membrane.
• Cellular RNAs may chaperone MA, preventing premature association with intracellular membranes.

Purpose of the Study:

• To investigate the direct binding interaction between the HIV-1 MA domain and the cytoplasmic tails (CTs) of Env trimers.
• To elucidate the role of MA trimerization and RNA binding in MA-CT interactions.
• To identify regions of Env CTs involved in MA binding.

Main Methods:

• Direct binding assays to demonstrate MA-CT interaction.
• Use of MA mutants, matrix-capsid (MACA) proteins, and inositol polyphosphate to study MA trimerization and CT binding.
• Assessment of RNA ligand effects on MA-CT binding.
• Rough-mapping studies to identify CT regions involved in MA binding.

Main Results:

• Direct binding assays confirmed that MA binds to Env CTs.
• MA-CT binding correlated with MA trimerization, suggesting MA lattices regulate CT interactions.
• High-affinity RNA ligands reduced MA-CT binding, indicating interference with MA trimerization or direct/indirect blocking of binding sites.
• C-terminal helices of Env CTs were implicated in MA binding.

Conclusions:

• HIV-1 Env trimers are captured in assembling PrGag lattices via binding to MA trimers.
• MA trimerization is a key factor in mediating MA-CT interactions.
• MA-RNA interactions can negatively regulate MA-CT binding, potentially via disruption of MA trimerization.
• Targeting MA-CT interactions represents a promising strategy for developing novel antiviral therapies against HIV-1.