Cortistatin A (CA) is a highly selective inhibitor of the Mediator kinases CDK8 and CDK19. Using CA, we report here the first large-scale identification of Mediator kinase substrates in human cells (HCT116). Among over 16,000 quantified phosphosites, we identified 78 high-confidence Mediator kinase targets within 64 proteins, including DNA-binding transcription factors and proteins associated with chromatin, DNA repair, and RNA polymerase II. Although RNA-Seq data correlated with Mediator kinase targets, CA effects on gene expression were limited and distinct from CDK8 or CDK19 knockdown. Quantitative proteome analyses, which tracked about 7,000 proteins across six time points (0 – 24h), revealed that CA selectively affected pathways implicated in inflammation, growth, and metabolic regulation; contrary to expectations, increased turnover of Mediator kinase targets was not generally observed. Collectively, these data support Mediator kinases as regulators of chromatin and RNA polymerase II activity and suggest cellular roles beyond transcription, including metabolism and DNA repair. Overall design: HCT116 cells were treated with either 100nM CA or DMSO in biological triplicate for each population (6 samples total). Treatment was for 24h for compound and vehicle.
Identification of Mediator Kinase Substrates in Human Cells using Cortistatin A and Quantitative Phosphoproteomics.
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View SamplesSuper-enhancers (SEs), which are composed of large clusters of enhancers densely loaded with the Mediator complex, transcription factors and chromatin regulators, drive high expression of genes implicated in cell identity and disease, such as lineage-controlling transcription factors and oncogenes. BRD4 and CDK7 are positive regulators of SE-mediated transcription. By contrast, negative regulators of SE-associated genes have not been well described. Here we show that the Mediator-associated kinases cyclin-dependent kinase 8 (CDK8) and CDK19 restrain increased activation of key SE-associated genes in acute myeloid leukaemia (AML) cells. We report that the natural product cortistatin A (CA) selectively inhibits Mediator kinases, has anti-leukaemic activity in vitro and in vivo, and disproportionately induces upregulation of SE-associated genes in CA-sensitive AML cell lines but not in CA-insensitive cell lines. In AML cells, CA upregulated SE-associated genes with tumour suppressor and lineage-controlling functions, including the transcription factors CEBPA, IRF8, IRF1 and ETV6. The BRD4 inhibitor I-BET151 downregulated these SE-associated genes, yet also has anti-leukaemic activity. Individually increasing or decreasing the expression of these transcription factors suppressed AML cell growth, providing evidence that leukaemia cells are sensitive to the dosage of SE-associated genes. Our results demonstrate that Mediator kinases can negatively regulate SE-associated gene expression in specific cell types, and can be pharmacologically targeted as a therapeutic approach to AML.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
Specimen part, Cell line, Treatment
View SamplesWe characterized the marine natural product cortistatin A (CA) as an inhibitor of CDK8 to determine whether pharmacologic inhibition of CDK8 regulates super-enhancer function and inhibits AML proliferation.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
Specimen part, Cell line, Treatment
View SamplesWe characterized the marine natural product cortistatin A (CA) as an inhibitor of CDK8 to determine whether pharmacologic inhibition of CDK8 regulates super-enhancer function and inhibits AML proliferation.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
Specimen part, Cell line, Treatment
View SamplesWe characterized the marine natural product cortistatin A (CA) as an inhibitor of CDK8 to determine whether pharmacologic inhibition of CDK8 regulates super-enhancer function and inhibits AML proliferation.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
Specimen part, Cell line, Treatment
View SamplesWe characterized the marine natural product cortistatin A (CA) as an inhibitor of CDK8 to determine whether pharmacologic inhibition of CDK8 regulates super-enhancer function and inhibits AML proliferation.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
Specimen part, Cell line, Treatment
View SamplesWe characterized the marine natural product cortistatin A (CA) as an inhibitor of CDK8 to determine whether pharmacologic inhibition of CDK8 regulates super-enhancer function and inhibits AML proliferation. In this series, we examine the transcriptional effect on insensitive HCT116 cells of 3hrs exposure to CA. Overall design: HCT116 cells were treated in triplicate with either DMSO or CA for 3hrs after which RNA was harvested and prepared for RNA sequencing to assess transcriptional changes.
Mediator kinase inhibition further activates super-enhancer-associated genes in AML.
No sample metadata fields
View SamplesThis SuperSeries is composed of the SubSeries listed below.
A formalin-fixed paraffin-embedded (FFPE)-based prognostic signature to predict metastasis in clinically low risk stage I/II microsatellite stable colorectal cancer.
Sex, Age
View SamplesThis study was conducted in order to identify biomarkers for a prognostic gene expression signature for metastases in early stage CRC.
A formalin-fixed paraffin-embedded (FFPE)-based prognostic signature to predict metastasis in clinically low risk stage I/II microsatellite stable colorectal cancer.
Sex, Age
View SamplesTranscriptome analysis of RNAs extracted from 2 hour-TGF-b-treated or untreated LX-2 cells with or without STAT3 knockdown
Transforming Growth Factor-β (TGF-β) Directly Activates the JAK1-STAT3 Axis to Induce Hepatic Fibrosis in Coordination with the SMAD Pathway.
Treatment, Time
View Samples