In vitro protease cleavage and computer simulations reveal the HIV-1 capsid maturation pathway

TL;DR

This study combines biochemical assays, cryoEM structural analysis, and computer simulations to elucidate the HIV-1 maturation pathway, revealing a sequential process involving both displacive and disassembly/reassembly mechanisms.

Contribution

It introduces an integrated approach using in vitro protease digestion, cryoEM, and simulations to clarify HIV-1 capsid formation, supporting a hybrid maturation model.

Findings

HIV-1 protease processing produces mature capsid components

Capsid assembly follows probable pathways revealed by simulations

Maturation involves both displacive and disassembly/reassembly processes

Abstract

HIV-1 virions assemble as immature particles containing Gag polyproteins that are processed by the viral protease into individual components, resulting in the formation of mature infectious particles. There are two competing models for the process of forming the mature HIV-1 core: the disassembly and de novo reassembly model and the non-diffusional displacive model. To study the maturation pathway, we simulate HIV-1 maturation in vitro by digesting immature particles and assembled virus-like particles with recombinant HIV-1 protease and monitor the process with biochemical assays and cryoEM structural analysis in parallel. Processing of Gag in vitro is accurate and efficient and results in both soluble capsid protein and conical or tubular capsid assemblies, seemingly converted from immature Gag particles. Computer simulations further reveal probable assembly pathways of HIV-1 capsid formation. Combining the experimental data and computer simulations, our results suggest a sequential combination of both displacive and disassembly/reassembly processes for HIV-1 maturation.