Résumé
Genome-wide CRISPR/Cas9 knock-out genetic screens are powerful approaches to unravelnew regulators of various cellular processes, including viral replication cycles. With the aim ofidentifying new cellular inhibitors of HIV-1, we have developed a whole-genome CRISPR/Cas9knock-out screen using the ability of type I interferon to potently inhibit HIV-1 infection in orderto create a cellular environment hostile to HIV-1 replication. This screen led to the identificationof the DEAD-box RNA helicase, DDX42, as an intrinsic inhibitor of HIV-1. Cells depleted forDDX42 became more susceptible to HIV-1 infection both in the presence and in the absenceof interferon. The ability of endogenous DDX42 to potently inhibit HIV-1 infection was observedin cell lines and in physiological targets of HIV-1, primary CD4+ T cells and monocyte-derivedmacrophages. Similarly, DDX42 overexpression potently inhibited HIV-1 infection. The positiveimpact of DDX42 depletion on HIV-1 infection was directly correlated to a substantial increasein viral DNA accumulation, pinpointing an inhibitory role of DDX42 on reverse transcription.Within cells, DDX42 was found primarily in the nucleus but was also present in the cytoplasm.Interestingly, proximity ligation assays showed that DDX42 was in the close vicinity of HIV-1Capsid during infection of primary monocyte-derived macrophages. Investigation on DDX42specificity showed that different lentiviruses, the retrovirus MLV and the retrotransposition ofLINE-1 were inhibited by DDX42. Finally, we reveal that DDX42 was able to decrease infectionwith a variety of viruses including alphaviruses, flaviviruses and coronaviruses.