CDK8 inhibitors antagonize HIV-1 reactivation and promote provirus latency in T cells

Abstract

Latent HIV-1 provirus represents a barrier towards a cure for infection, but is dependent upon the host RNA Pol II machinery for expression. We find that inhibitors of the RNA Pol II mediator kinases CDK8/19, Senexin A and BRD6989, inhibit induction of HIV-1 expression in response to latency reversing agents and T cell signaling agonists. These inhibitors were found to impair recruitment of RNA Pol II to HIV-1 LTR. HIV-1 expression in response to several latency reversal agents was impaired upon disruption of CDK8 by shRNA or gene knockout. However, the effects of CDK8 depletion did not entirely mimic CDK8/19 kinase inhibition suggesting that the mediator kinases are not functionally redundant. Furthermore, treatment of CD4+ PBMCs isolated from people living with HIV-1 and who are receiving ART with Senexin A inhibited induction of virus replication in response to T cell stimulation by PMA and ionomycin. These observations indicate that the mediator kinases CDK8 and CDK19, play a significant role for regulation of HIV-1 transcription, and that small molecule inhibitors of these enzymes may contribute to therapies designed to promote deep latency involving the durable suppression of provirus expression.

Small molecule inhibitors of transcriptional Cyclin Dependent Kinases impose HIV-1 latency, presenting “block and lock” treatment strategies

“…4 A , 4 B ). In agreement with previous reports (Horvath et al , 2023), we observed a vigorous synergistic interaction between PEP005 activation of NFκB and IACS-9571 inhibition of the TRIM24 bromodomain (Fig. S3).…”

“…The function of CDK8/19 is not dependent on Tat (Fig 5, Fig. S4), consistent with previous findings that CDK8/19 inhibition limits reactivation of ACH2 and U1 proviral latency cell models (Horvath et al , 2023). Additionally, we display a synergistic interaction between the CDK8/19 inhibitor Senexin A and inhibitors of either CDK7 or CDK9, suggesting distinct mechanism(s) of action.…”

“…Ingenol 3-angelate (PEP005) activates PKC-NFκB, partially mimicking T cell activation (Kedei et al , 2004). JQ1 and IACS-9571 are bromodomain inhibitors that reverse latency as mediated by their respective targets, BRD4 (Li et al, 2013) and TRIM24 (Horvath et al , 2023). Finally, suberanilohydroxamic acid (SAHA) is a well-studied histone deacetylase inhibitor (HDACi) known to reactivate HIV-1 expression in vitro and in vivo (Contreras et al , 2009) (Desimio et al , 2017).…”

“…Recently, work from our lab has identified that CDK8 is a coactivator of HIV-1 expression and small molecule inhibition of CDK8/19 kinase activity restricts proviral reactivation (Horvath et al , 2023). Similarly, here we show that Senexin A inhibition of CDK8/19 suppresses viral induction in response to a diverse set of LRAs (Fig.…”

“…Bliss independence modeling was used as previously described (Horvath et al , 2023) to statistically assess the inhibitory activity of combinatorial tCDK inhibitor treatment on HIV-1 reactivation. The equation Fa xy, P = Fa x + Fa y – ( Fa x )( Fa y ) defines the Bliss independence model, in which Fa xy, P is the predicted fraction affected by a combination of drug x and drug y that is derived from the experimentally observed fraction affected by drug x ( Fa x ) and drug y ( Fa y ) individually.…”