New BRD4-inhibitor quinoline compound targets a distinct latent HIV-1 reservoir for re-activation from canonical “shock” drugs

Upon HIV-1 infection, a reservoir of latently infected resting T cells prevents the eradication of the virus from patients. To achieve complete depletion, the existing virus-suppressing antiretroviral therapy must be combined with drugs that reactivate the dormant viruses. We previously described a novel chemical scaffold compound, MMQO (8-methoxy-6-methylquinolin-4-ol) that is able to reactivate viral transcription in J-Lat T cell model of latency through an unknown mechanism. Here we demonstrate that MMQO activates HIV-1 in ex vivo latently infected primary CD4 T cells, where it synergizes with the PKC agonist prostratin. Gene expression microarray analysis in Jurkat cells indicated that MMQO treatment results in robust immunosuppression, affects cell proliferation by rapidly diminishing expression of the transcription factor c-Myc, and causes the dysregulation of acetylation sensitive genes. These hallmarks indicated that MMQO mimics acetylated lysines of core histones and might function as a bromodomain and extraterminal domain protein family inhibitor (BETi). MMQO functionally mimics the effects of JQ1, a well-known BETi. We confirmed that MMQO interacts with the BET family bromodomain BRD4. Utilizing MMQO and JQ1, we demonstrate how the inhibition of BRD4 targets a distinct subset of latently integrated barcoded proviruses from those targeted by HDAC inhibitors or PKC pathway agonists. Thus, the scaffold compound MMQO is a new member of the BET family inhibitors, which due to its minimalistic structure holds promise for further optimization for increased affinity and specificity for distinct bromodomain family members and could potentially be of use against a variety of diseases, including HIV. We used the system of Jurkat T cells with latent barcoded HIV infections and measured the fold induction of HIV expression by the drugs including MMQO, JQ1, Prostratin and SAMA through the B-HIVE technology. Each sample preparation and data analysis was done in parallel in 2 replicates. DMSO treatment as a negative control.