Specific Interaction of DARPin with HIV-1 CA NTD Disturbs the Distribution of Gag, RNA Packaging, and Tetraspanin Remodelling in the Membrane.

A designed repeat scaffold protein (Ank GAG 1D4) recognizing the human immunodeficiency virus-1 (HIV-1) capsid (CA) was formerly established with antiviral assembly. Here, we investigated the molecular mechanism of Ank GAG 1D4 function during the late stages of the HIV-1 replication cycle. By applying stimulated emission-depletion (STED) microscopy, Gag polymerisation was interrupted at the plasma membrane. Disturbance of Gag polymerisation triggered Gag accumulation inside producer cells and trapping of the CD81 tetraspanin on the plasma membrane. Moreover, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) experiments were performed to validate the packaging efficiency of RNAs. Our results advocated that Ank GAG 1D4 interfered with the Gag precursor protein from selecting HIV-1 and cellular RNAs for encapsidation into viral particles. These findings convey additional information on the antiviral activity of Ank GAG 1D4 at late stages of the HIV-1 life cycle, which is potential for an alternative anti-HIV molecule.