The Three-Fold Axis of the HIV-1 Capsid Lattice Is the Species-Specific Binding Interface for TRIM5α.

Damien Morger,Benjamin Schuler,Maximilian Mittelviefhaus,Martin Bühlmann,Franziska Zosel,Markus G Grütter,Sara Züger,Jeremy Luban,Frank Kirchhoff

doi:10.1128/jvi.01541-17

Abstract

ABSTRACTRhesus TRIM5α (rhTRIM5α) potently restricts replication of human immunodeficiency virus type 1 (HIV-1). Restriction is mediated through direct binding of the C-terminal B30.2 domain of TRIM5α to the assembled HIV-1 capsid core. This host-pathogen interaction involves multiple capsid molecules within the hexagonal HIV-1 capsid lattice. However, the molecular details of this interaction and the precise site at which the B30.2 domain binds remain largely unknown. The human orthologue of TRIM5α (hsTRIM5α) fails to block infection by HIV-1 both in vivo and in vitro. This is thought to be due to differences in binding to the capsid lattice. To map the species-specific binding surface on the HIV-1 capsid lattice, we used microscale thermophoresis and dual-focus fluorescence correlation spectroscopy to measure binding affinity of rhesus and human TRIM5α B30.2 domains to a series of HIV-1 capsid variants that mimic distinct capsid arrangements at each of the symmetry axes of the HIV-1 capsid lattice. These surrogates include previously characterized capsid oligomers, as well as a novel chemically cross-linked capsid trimer that contains cysteine substitutions near the 3-fold axis of symmetry. The results demonstrate that TRIM5α binding involves multiple capsid molecules along the 2-fold and 3-fold interfaces between hexamers and indicate that the binding interface at the 3-fold axis contributes to the well-established differences in restriction potency between TRIM5α orthologues.IMPORTANCE TRIM5α is a cellular protein that fends off infection by retroviruses through binding to the viruses' protein shell surrounding its genetic material. This shell is composed of several hundred capsid proteins arranged in a honeycomb-like hexagonal pattern that is conserved across retroviruses. By binding to the complex lattice formed by multiple capsid proteins, rather than to a single capsid monomer, TRIM5α restriction activity persists despite the high mutation rate in retroviruses such as HIV-1. In rhesus monkeys, but not in humans, TRIM5α confers resistance to HIV-1. By measuring the binding of human and rhesus TRIM5α to a series of engineered HIV-1 capsid mimics of distinct capsid lattice interfaces, we reveal the HIV-1 capsid surface critical for species-specific binding by TRIM5α.

Highlights

Rhesus TRIM5␣ potently restricts replication of human immunodeficiency virus type 1 (HIV-1)
In order to characterize binding of TRIM5␣ to the retroviral capsid surface, we produced oligomeric HIV-1 capsid molecules that mimic distinct capsid arrangements of the assembled HIV-1 capsid lattice (Fig. 1a): the wild-type, full-length HIV-1 capsid protein which forms dimers in solution [37], the monomeric HIV-1 capsid N-terminal domain (NTD) without the C-terminal dimerization domain (CTD), the disulfide-stabilized hexameric capsid as described by Pornillos et al [38], and a trimeric HIV-1 capsid that resembles an arrangement around the 3-fold axis of the capsid lattice (Fig. 1b)
The proximal capsid NTDs form a surface that is accessible to TRIM5 binding, while the capsid CTDs are located on the inside of the HIV-1 capsid core

Summary

Introduction

Rhesus TRIM5␣ (rhTRIM5␣) potently restricts replication of human immunodeficiency virus type 1 (HIV-1). To map the species-specific binding surface on the HIV-1 capsid lattice, we used microscale thermophoresis and dual-focus fluorescence correlation spectroscopy to measure binding affinity of rhesus and human TRIM5␣ B30.2 domains to a series of HIV-1 capsid variants that mimic distinct capsid arrangements at each of the symmetry axes of the HIV-1 capsid lattice. By its specificity for the common hexagonal lattice pattern of retroviral capsids, TRIM5␣ can recognize a broad range of retroviral cores of highly variable primary structures [11, 20,21,22,23,24,25,26,27] This allows TRIM5␣ to remain restrictive despite the high mutation rate of retroviruses. The structural basis for capsid recognition at the crucial step of binding remains elusive

Methods

Results

Conclusion