Inhibition of HIV-1 Gag-membrane interactions by specific RNAs

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• HIV-1 particle assembly is crucial for viral replication and occurs at the host cell's plasma membrane.
• The viral Gag polyprotein mediates assembly by binding to phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P2) via its matrix (MA) domain's highly basic region (HBR).
• The HBR also interacts with RNA, and RNA has been shown to inhibit Gag binding to membranes lacking PI(4,5)P2.

Purpose of the Study:

• To identify specific RNA species responsible for inhibiting HIV-1 Gag protein's interaction with negatively charged membranes.
• To elucidate the mechanism by which RNA influences Gag-membrane binding.

Main Methods:

• In vitro liposome binding assays were employed to test the effects of purified RNAs on Gag-liposome interactions.
• Various RNA species, including tRNAs and specific HIV-1 genomic fragments, were tested for their inhibitory capacity.
• Mutational analysis of the Gag protein (HBR and NC domain) was performed to assess their roles in RNA-mediated inhibition.

Main Results:

• Certain tRNA species and HIV-1 psi RNAs (stem-loop 1) significantly inhibited Gag binding to liposomes lacking PI(4,5)P2.
• A subset of tRNAs and an in vitro selected MA-binding RNA did not suppress Gag-membrane interactions.
• Deletion of the NC domain in Gag abrogated RNA-mediated inhibition, while mutations in the HBR did not affect susceptibility to RNA inhibition.

Conclusions:

• The Gag NC domain plays a critical role in facilitating RNA binding to the MA domain.
• This RNA-MA interaction, mediated by NC, leads to the inhibition of Gag binding to cellular membranes.
• These findings support a model where specific RNAs regulate HIV-1 Gag membrane association, potentially influencing viral assembly.