Permeability of the HIV-1 capsid to metabolites modulates viral DNA synthesis.

• Main Authors: Chaoyi Xu, Douglas K Fischer, Sanela Rankovic, Wen Li, Robert A Dick, Brent Runge, Roman Zadorozhnyi, Jinwoo Ahn, Christopher Aiken, Tatyana Polenova, Alan N Engelman, Zandrea Ambrose, Itay Rousso, Juan R Perilla
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2020-12-01
• Series: PLoS Biology
• Online Access: https://doi.org/10.1371/journal.pbio.3001015

Reverse transcription, an essential event in the HIV-1 life cycle, requires deoxynucleotide triphosphates (dNTPs) to fuel DNA synthesis, thus requiring penetration of dNTPs into the viral capsid. The central cavity of the capsid protein (CA) hexamer reveals itself as a plausible channel that allows the passage of dNTPs into assembled capsids. Nevertheless, the molecular mechanism of nucleotide import into the capsid remains unknown. Employing all-atom molecular dynamics (MD) simulations, we established that cooperative binding between nucleotides inside a CA hexamer cavity results in energetically favorable conditions for passive translocation of dNTPs into the HIV-1 capsid. Furthermore, binding of the host cell metabolite inositol hexakisphosphate (IP6) enhances dNTP import, while binding of synthesized molecules like benzenehexacarboxylic acid (BHC) inhibits it. The enhancing effect on reverse transcription by IP6 and the consequences of interactions between CA and nucleotides were corroborated using atomic force microscopy, transmission electron microscopy, and virological assays. Collectively, our results provide an atomistic description of the permeability of the HIV-1 capsid to small molecules and reveal a novel mechanism for the involvement of metabolites in HIV-1 capsid stabilization, nucleotide import, and reverse transcription.