PRJNA542065
Transcriptional responses to interferon require Mediator kinase-dependent pause release and mechanistically distinct functions of CDK8 and CDK19
Transcriptional responses to external stimuli remain poorly understood. Using GRO-Seq and PRO-Seq, we show that CDK8 kinase activity promotes RNA polymerase II (RNAPII) pause release in response to IFN-?, a universal cytokine involved in immunity and tumor surveillance. The Mediator kinase module contains CDK8 or CDK19, which are presumed to be functionally redundant. We implemented cortistatin A, chemical genetics, transcriptomics, and other methods to de-couple their function while assessing enzymatic vs. structural roles. Unexpectedly, CDK8 and CDK19 regulated different gene sets via distinct mechanisms. CDK8-dependent regulation required its kinase activity, whereas CDK19 governed IFN-? responses through its scaffolding function (i.e. kinase-independent). Accordingly, CDK8, not CDK19, phosphorylates the STAT1 transcription factor (TF) during IFN-? stimulation, and Mediator kinase inhibition blocked activation of JAK-STAT pathway TFs. These results establish CDK8 as a regulator of RNAPII promoter-proximal pausing and suggest separate CDK8 and CDK19 targeting as a therapeutic strategy to modulate IFN-? responses.