DEAD-box RNA helicase DDX3 connects CRM1-dependent nuclear export and translation of the HIV-1 unspliced mRNA through its N-terminal domain

•The N-terminal and helicase domains of DDX3 are sufficient to support HIV-1 unspliced mRNA translation.•DDX3 activity during HIV-1 and HIV-2 unspliced mRNA translation is specifically regulated through the N-terminal domain.•The N-terminal domain of DDX3 interconnects CRM1-dependent nuclear export with translation of the HIV-1 unspliced mRNA.•Intrinsic disorder is characteristic of the N- and C-terminal domains of human DEAD-box proteins and DDX3 homologs.

DEAD-box RNA helicase DDX3 is a host factor essential for HIV-1 replication and thus, a potential target for novel therapies aimed to overcome viral resistance. Previous studies have shown that DDX3 promotes nuclear export and translation of the HIV-1 unspliced mRNA. Although the function of DDX3 during both processes requires its catalytic activity, it is unknown whether other domains surrounding the helicase core are involved. Here, we show the involvement of the N- and C-terminal domains of DDX3 in the regulation of HIV-1 unspliced mRNA translation. Our results suggest that the intrinsically disordered N-terminal domain of DDX3 regulates its functions in translation by acting prior to the recruitment of the 43S pre-initiation complex onto the viral 5′-UTR. Interestingly, this regulation was conserved in HIV-2 and was dependent on the CRM1-dependent nuclear export pathway suggesting a role of the RNA helicase in interconnecting nuclear export with ribosome recruitment of the viral unspliced mRNA. This specific function of DDX3 during HIV gene expression could be exploited as an alternative target for pharmaceutical intervention.