Elements in HIV-1 Gag contributing to virus particle assembly

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• The Gag polyprotein is essential for retroviral particle assembly.
• Nucleic acid (NA) is required for in vitro HIV-1 Gag assembly, potentially by promoting Gag oligomerization.
• The Gag protein has matrix (MA), capsid (CA), nucleocapsid (NC), and p6 domains, with the SP1 linker between CA and NC.

Purpose of the Study:

• To investigate alternative pathways for Gag assembly in the absence of NC-RNA binding.
• To determine the roles of Gag-membrane binding, Gag dimer interface, and NC-RNA binding in HIV-1 Gag assembly.
• To understand the minimal requirements for Gag oligomerization and virus-like particle formation.

Main Methods:

• Construction and analysis of HIV-1 Gag mutants with disrupted Gag-membrane binding, Gag dimer interface, or NC-RNA binding.
• Assessing virus-like particle formation in cells using these mutants.
• Evaluating the impact of combined mutations on Gag assembly.

Main Results:

• Disruption of any single interaction (Gag-membrane, Gag dimer, or NC-RNA binding) did not prevent Gag assembly.
• Simultaneous disruption of any two of these three interaction types completely abolished Gag assembly.
• HIV-1 Gag assembly can be rescued by alternative interactions when one pathway is blocked.

Conclusions:

• HIV-1 Gag utilizes at least three distinct interaction types to form oligomers necessary for assembly.
• Any two of the three identified interaction pathways (Gag-membrane, Gag dimer, NC-RNA binding) are sufficient for Gag assembly.
• This redundancy in assembly mechanisms highlights the adaptability of retroviral particle formation.