Journal Article

HIV-1 uses dynamic capsid pores to import nucleotides and fuel encapsidated DNA synthesis

McEwan, William A., Price, Amanda J., James, Leo C., Hilditch, Laura, Jacques, David A., Towers, Greg J.

2016

Overview

Size-selective pores in the HIV-1 capsid hexamer recruit nucleotides, thereby allowing reverse transcription to take place inside the capsid. Capsid pores key to HIV-1 proliferation Recent work has suggested that HIV-1 evades innate DNA sensors such as cGAS by enclosing the viral genome inside a protective protein shell, the capsid. If the virus is to establish infection, however, it needs to be able to synthesize DNA. Leo James and colleagues show that HIV-1 sustains DNA synthesis inside the capsid by importing nucleotides through dynamic size-selective pores. The authors use structural, biophysical and virological methods to characterize these pores and find that they are highly efficient nucleotide pumps. The channel inhibitor hexacarboxybenzene is shown to block encapsidated reverse transcription, demonstrating the potential of the pore as an antiretroviral drug target. During the early stages of infection, the HIV-1 capsid protects viral components from cytosolic sensors and nucleases such as cGAS and TREX, respectively, while allowing access to nucleotides for efficient reverse transcription 1 . Here we show that each capsid hexamer has a size-selective pore bound by a ring of six arginine residues and a ‘molecular iris’ formed by the amino-terminal β-hairpin. The arginine ring creates a strongly positively charged channel that recruits the four nucleotides with on-rates that approach diffusion limits. Progressive removal of pore arginines results in a dose-dependent and concomitant decrease in nucleotide affinity, reverse transcription and infectivity. This positively charged channel is universally conserved in lentiviral capsids despite the fact that it is strongly destabilizing without nucleotides to counteract charge repulsion. We also describe a channel inhibitor, hexacarboxybenzene, which competes for nucleotide binding and efficiently blocks encapsidated reverse transcription, demonstrating the tractability of the pore as a novel drug target.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 13/31 / 38/70 / 38/77 / 631/326/596/1787 / 631/45/535/1266 / 631/92/612/1256 / 82/80 / 82/83 / 88/16 / 96/34 / Arginine - metabolism / Benzoates - pharmacology / Binding, Competitive - drug effects / Biological Transport, Active - drug effects / Capsid - chemistry / Capsid - drug effects / Capsid - metabolism / Crystal structure / Deoxyribonucleic acid / Diffusion / DNA / DNA Replication - drug effects / DNA, Viral - biosynthesis / HEK293 Cells / HeLa Cells / HIV / HIV-1 - drug effects / HIV-1 - genetics / HIV-1 - growth & development / HIV-1 - metabolism / Human immunodeficiency virus / Humanities and Social Sciences / Humans / Kinetics / letter / Models, Molecular / multidisciplinary / Nucleotides - metabolism / Porosity - drug effects / Proteins / Reverse Transcription - drug effects / Science / Virology