Blocking Host Factors IAP and DDX3 Activates HIV-1 Transcription and Increases Apoptosis Sensitivity of HIV-1 Infected Cells

Antiretroviral therapy (ART) effectively suppresses HIV-1 replication but does not purge the latent HIV-1 reservoir. Strategies aimed at HIV-1 latency reversal and subsequent elimination of infected cells are being explored. Targeting the inhibitor of apoptosis proteins (IAP) and DEAD-box polypeptide 3 (DDX3) RNA helicase reduces the HIV-1 reservoir ex vivo. However, the mechanisms driving apoptosis of HIV-1 infected cells remain unclear. Here, we uncovered the mechanism regarding HIV-1 transcriptional activation and induction of apoptosis specific for HIV-1 infected cells using an acute in vitro infection model. Inhibition of IAP by second mitochondrial-derived activator of caspases mimetic (SMACm; AZD5582) resulted in activation of non-canonical NF-κB pathway (RelB/p52) that induced HIV-1 transcription, confirming previous reports, whereas inhibition of DDX3 sensitized HIV-1 infected cells for apoptosis (DDX3i; FH1321). Transcriptome analysis revealed that HIV-1 actively suppressed apoptosis-related genes in HIV-1 infected cells. SMACm treatment resulted in a broad induction of these genes irrespective of infection. Notably, DDX3 inhibition specifically restored the expression of the majority of HIV-1 suppressed genes, and when combined with SMACm, restored almost all HIV-1 downregulated genes, thereby rendering HIV-1 infected cells sensitive to apoptosis. Thus, our data strongly suggest that inhibition of host factors IAP and DDX3 not only induces activation of HIV-1 transcription but also restores HIV-1 suppressed apoptotic processes in infected cells.