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Published June 2, 2016 | Published + Supplemental Material
Journal Article Open

Primate TRIM5 proteins form hexagonal nets on HIV-1 capsids


TRIM5 proteins are restriction factors that block retroviral infections by binding viral capsids and preventing reverse transcription. Capsid recognition is mediated by C-terminal domains on TRIM5α (SPRY) or TRIMCyp (cyclophilin A), which interact weakly with capsids. Efficient capsid recognition also requires the conserved N-terminal tripartite motifs (TRIM), which mediate oligomerization and create avidity effects. To characterize how TRIM5 proteins recognize viral capsids, we developed methods for isolating native recombinant TRIM5 proteins and purifying stable HIV-1 capsids. Biochemical and EM analyses revealed that TRIM5 proteins assembled into hexagonal nets, both alone and on capsid surfaces. These nets comprised open hexameric rings, with the SPRY domains centered on the edges and the B-box and RING domains at the vertices. Thus, the principles of hexagonal TRIM5 assembly and capsid pattern recognition are conserved across primates, allowing TRIM5 assemblies to maintain the conformational plasticity necessary to recognize divergent and pleomorphic retroviral capsids.

Additional Information

© 2016, Li et al. This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited. Received March 22, 2016. Accepted May 19, 2016. Published June 02, 2016. Deep-etch electron microscopy was performed by Robyn Roth and John Heuser at the Laboratory of Electron Microscopy Sciences, Department of Cell Biology, Washington University School of Medicine. We are grateful to Ruth Pumroy for contributing TRIM5 proteins used in our co-assembly assays and to members of our laboratories for helpful discussions and critical reading of the manuscript. This work was supported by funds from NIH NIGMS P50 082545 (to MY, BKG-P GJJ and WIS). Competing interests: Wesley I Sundquist, Reviewing editor, eLife. The other authors declare that no competing interests exist.

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