RanBP2 regulates the anti-retroviral activity of TRIM5\u03b1 by SUMOylation at a predicted phosphorylated SUMOylation motif

Ghizlane Maarifi,Débora M. Portilho,Aude Boulay,Stéphane Oddos,Gillian Butler-Browne,Juliette Fernandez,Sébastien Nisole,Nathalie J. Arhel,Jacques Dutrieux

doi:10.1038/s42003-018-0198-0

Abstract

TRIM5α is a cytoplasmic restriction factor that blocks post-entry retroviral infection. Evidence suggests that its antiviral activity can be regulated by SUMO, but how this is achieved remains unknown. Here, we show that TRIM5α forms a complex with RanGAP1, Ubc9, and RanBP2 at the nuclear pore, and that RanBP2 E3 SUMO ligase promotes the SUMOylation of endogenous TRIM5α in the cytoplasm. Loss of RanBP2 blocked SUMOylation of TRIM5α, altered its localization in primary cells, and suppressed the antiviral activity of both rhesus and human orthologs. In cells, human TRIM5α is modified on K84 within a predicted phosphorylated SUMOylation motif (pSUM) and not on K10 as found in vitro. Non-modified TRIM5α lacked antiviral activity, indicating that only SUMOylated TRIM5α acts as a restriction factor. This work illustrates the importance of the nuclear pore in intrinsic antiviral immunity, acting as a hub where virus, SUMO machinery, and restriction factors can meet.

Highlights

TRIM5α is a cytoplasmic restriction factor that blocks post-entry retroviral infection
Some have shown co-localization of overexpressed TRIM5α with Promyelocytic Leukaemia Nuclear Bodies (PML-NB)[13,14], which are a preferred site of SUMOylation and harbor many proteins of the small ubiquitin-related modifiers (SUMO) machinery, including SUMO and PIAS115,16, we could not reproduce these findings with endogenous TRIM5α13
We show that TRIM5α associates with RanGAP1, RanBP2, and Ubc[9] at the nuclear pore, and is SUMO conjugated by the nucleoporin and E3 SUMO ligase RanBP2 within this complex

Summary

Introduction

TRIM5α is a cytoplasmic restriction factor that blocks post-entry retroviral infection. We show that TRIM5α forms a complex with RanGAP1, Ubc[9], and RanBP2 at the nuclear pore, and that RanBP2 E3 SUMO ligase promotes the SUMOylation of endogenous TRIM5α in the cytoplasm. Restriction factors are antiviral proteins produced by the host to antagonise viral infection They are considered the first line of defence against viruses, and can intervene literally within minutes of cell entry, to either degrade the virus or block its replication. Treatment with ginkgolic acid, an inhibitor of the E1 SUMO-activating enzyme, reduces nuclear residency of TRIM5α13, suggesting that TRIM5α is SUMO modified in the cytoplasm and shuttles to the nucleus as a SUMOylated protein.

Methods

Results

Conclusion