HTLV-1 Rex hijacks UPF1 in a CRM1 dependent manner, leading to NMD inhibition and revealing unexpected proviral roles of UPF1

Abstract

AbstractThe hijacking of CRM1 export is an important step of the retroviral replication cycle. Here, we investigated the consequences of this hijacking for the host. During HTLV-1 infection, we identified the formation of a complex composed of Rex, CRM1 and the RNA helicase UPF1, leading to the nuclear retention of UPF1. We further showed how this leads to the inhibition of the nonsense mediated mRNA decay (NMD), known to have an antiviral function. Corroborating these results, we described a similar process with Rev, the functional homolog of Rex from HIV-1. Unexpectedly, we also found that, for HTLV-1, this process is coupled with the specific loading of UPF1 onto vRNA, independently of NMD. In this latter context, UPF1 positively regulates several steps of the viral replication cycle, from the nuclear export of vRNA to the production of mature viral particles.