부산대학교 도서관

Inhibitors of bromodomain and extra-terminal proteins (iBETs), including JQ-1, have been suggested as potential prophylactics against SARS-CoV-2 infection. However, molecular mechanisms underlying JQ-1-mediated antiviral activity and its susceptibility to viral subversion remain incompletely understood. Pretreatment of cells with iBETs inhibited infection by SARS-CoV-2 variants and SARS-CoV, but not MERS-CoV. The antiviral activity manifested itself by reduced reporter expression of recombinant viruses, and reduced viral RNA quantities and infectious titers in the culture supernatant. While we confirmed JQ-1-mediated downregulation of expression of angiotensin-converting enzyme 2 (ACE2) and interferon-stimulated genes (ISGs), multi-omics analysis addressing the chromatin accessibility, transcriptome and proteome uncovered induction of an antiviral nuclear factor erythroid 2-related factor 2 (NRF-2)-mediated cytoprotective response as an additional mechanism through which JQ-1 inhibits SARS-CoV-2 replication. Pharmacological inhibition of NRF-2, and knockdown of NRF-2 and its target genes reduced JQ-1-mediated inhibition of SARS-CoV-2 replication. Serial passaging of SARS-CoV-2 in the presence of JQ-1 resulted in predominance of ORF6-deficient variant, which exhibited resistance to JQ-1 and increased sensitivity to exogenously administered type I interferon (IFN-I), suggesting a minimised need for SARS-CoV-2 ORF6-mediated repression of IFN signalling in the presence of JQ-1. Importantly, JQ-1 exhibited a transient antiviral activity when administered prophylactically in human airway bronchial epithelial cells (hBAECs), which was gradually subverted by SARS-CoV-2, and no antiviral activity when administered therapeutically following an established infection. We propose that JQ-1 exerts pleiotropic effects that collectively induce an antiviral state in the host, which is ultimately nullified by SARS-CoV-2 infection, raising questions about the clinical suitability of the iBETs in the context of COVID-19. Author summary: The COVID-19 pandemic has sparked interest in the therapeutic potential of iBETs, which was already being pursued to inhibit proliferation of cancer cells and reactivate HIV-1 latency. Prior studies reported that prophylactic administration of iBETs inhibits SARS-CoV-2 replication by downregulating ACE2 expression. However, a subsequent study reported that therapeutic administration of iBETs enhanced SARS-CoV-2 replication by inhibiting induction of the IFN signalling pathway. Despite this controversy, susceptibility of iBET-mediated anti-SARS-CoV-2 activity to viral subversion remains unknown. Here, we found that despite inhibiting the IFN signalling pathway, prophylactic administration of JQ-1 triggers a multi-pronged but transient anti-SARS-CoV-2 activity by downregulating ACE2 expression and inducing NRF-2-mediated cytoprotective response. This antiviral activity is limited to the Sarbecoviruses, as MERS-CoV was resistant. In contrast, therapeutic administration of JQ-1 did not inhibit SARS-CoV-2 replication. An ORF6-deficient variant—which exhibited resistance to JQ-1 and enhanced sensitivity to IFN-I treatment—emerged following serial passaging of SARS-CoV-2 under increasing concentrations of JQ-1. This work illuminates the imperfections of iBETs as potential candidates against COVID-19, but lays the foundation for their exploitation to steer SARS-CoV-2 virions towards IFN evolutionary traps and facilitate immune clearance. [ABSTRACT FROM AUTHOR]