Transportin-1 (TRN-1) orchestrates HIV-1 uncoating and nuclear import

Timely uncoating and nuclear import are key to efficient HIV infection, however the triggers and mechanisms that orchestrate these steps are unknown. Here we show that HIV-1 exploits Transportin-1/TRN-1 for both uncoating and nuclear import. Depletion of TRN-1, which we characterised by mass spectrometry, significantly reduced the early steps of HIV-1 infection in cell lines and primary CD4+ T cells. We showed that TRN-1 binds to incoming HIV-1 capsid (CA) cores, but not monomeric CA or integrase, via a NLS present on the cyclophilin A (CypA) binding loop. The G89V mutant, but not P90A, relieved dependency on TRN-1, and TRN-1 binding to CA at position G89 displaced CypA, which likely contributes to weakening the CA assembly. Recombinant TRN-1 could induce CA uncoating in vitro indicating that disruption is entirely mechanical, and activity mapped to residue W730 that plays a pivotal role in binding to substrate NLS. HIV-1 intercepts TRN-1 near the nuclear envelope and complexes that fail to do so scatter back into the cytoplasm without uncoating. For complexes that uncoat, TRN-1 mediates the concomitant nuclear import of CA and viral DNA. Our study reveals how HIV-1 uses a single cellular protein to orchestrate the key steps that allow it to reach its replication compartment efficiently.