Project description:CDK7 associates with the 10-subunit TFIIH complex and regulates transcription by phosphorylating the C-terminal domain (CTD) of RNA polymerase II (RNAPII). Few additional CDK7 substrates are known. Here, using the covalent inhibitor SY-351 and quantitative phosphoproteomics, we identified CDK7 kinase substrates in human cells. Among hundreds of high-confidence targets, the vast majority are unique to CDK7 (i.e. distinct from other transcription-associated kinases), with a subset that suggest novel cellular functions. Transcription-associated factors were predominant CDK7 substrates, including SF3B1, U2AF2, and other splicing components. Accordingly, widespread and diverse splicing defects, such as alternative exon inclusion and intron retention, were characterized in CDK7-inhibited cells. Combined with biochemical assays, we establish that CDK7 directly activates other transcription-associated kinases CDK9, CDK12, and CDK13, invoking a “master regulator” role in transcription. We further demonstrate that TFIIH restricts CDK7 kinase function to the RNAPII CTD, whereas other substrates (e.g. SPT5, SF3B1) are phosphorylated by the 3-subunit CDK-activating kinase (CAK; CCNH, MAT1, CDK7). These results suggest new models for CDK7 function in transcription and implicate CAK dissociation from TFIIH as essential for kinase activation. This straightforward regulatory strategy ensures CDK7 activation is spatially and temporally linked to transcription, and may apply toward other transcription-associated kinases.
Project description:CDK7 phosphorylates the RNA polymerase II (pol II) CTD and activates the P-TEFb- associated kinase, CDK9, but its regulatory roles remain obscure. Using human CDK7 analog-sensitive (CDK7as) cells, we observed reduced capping enzyme recruitment, increased pol II promoter-proximal pausing, and defective termination at gene 3'-ends upon CDK7 inhibition. We also found that CDK7 regulates chromatin modifications downstream of transcription start sites. H3K4me3 spreading was restricted at gene 5'-ends and H3K36me3 was displaced toward gene 3'-ends in CDK7as cells. Together, these results implicate a CDK7-dependent "CTD code" that regulates epigenetic marks in addition to RNA processing and pol II pausing.
Project description:CDK7 is a cycline-dependent kinase part of the basal transcription factor TFIIH involved in the formation of the pre-inithiation complex of RNApol II dependent-genes. Despite it's well known genomic localization at the level of gene's promoter, it has been recently observed from Kwiatkowski et al., (2014) that CDK7 can be found also in large clusters of gene regulatory elements called Super-enhancers (SEs) of both normal and cancer cells. Here we report that CDK7 is resembling such distribution in a human melanoma context, in particular at the level of genes important in melanoma physiology such as the master transcription factors MITF and SOX10 which indeed, following the inhibition of CDK7 with the molecule THZ1, are rapidly downregulated at very low nanomolar concentration.
Project description:Cyclin-dependent kinase 7 (CDK7) plays a critical role in the general regulation of RNA polymerase II-mediated transcription. However, the absence of selective CDK7 inhibitors has hindered the ability to investigate the consequences of acute and prolonged inhibition of CDK7 under normal and pathological conditions. Here we present the discovery and characterization of the first covalent CDK7 inhibitor, CDK7-IN-1, that has the unprecedented ability to target a unique cysteine residue located outside of the canonical kinase domain, providing an unanticipated means of achieving selectivity for CDK7 amongst the 20 known CDKs. Cancer cell line profiling indicates that a subset of cancer cell lines, including T-cell acute lymphoblastic leukemia (T-ALL), exhibit 100-fold greater sensitivity to CDK7-IN-1 over other tumor and normal cell lines. Genome-wide expression analysis in Jurkat T-ALL indicates that CDK7-IN-1 disproportionally affects RUNX1 as well as other components of the TAL1 transcriptional network and its targets, downregulating key regulators of transcription and apoptosis critical for the T-ALL state. These oncogenes are encoded by short-lived mRNA transcripts, are associated with super-enhancers, and exhibit a strong dependency on continuous transcription for sustained expression. Therefore, pharmacological modulation of CDK7 kinase activity may define a method for the identification and treatment of tumor types exhibiting extreme dependencies on transcription for maintenance of the oncogenic state. Jurkat cells were treated with various drugs including a covalent inhibitor of CDK7 (CDK7-IN-1), a reversible inhibitor of CDK7 (CDK7-IN-1), Flavopiridol, Actinomycin D, and DMSO controls. Replicates are annotated.
Project description:Cyclin-dependent kinase 7 (CDK7) plays a critical role in the general regulation of RNA polymerase II-mediated transcription. However, the absence of selective CDK7 inhibitors has hindered the ability to investigate the consequences of acute and prolonged inhibition of CDK7 under normal and pathological conditions. Here we present the discovery and characterization of the first covalent CDK7 inhibitor, CDK7-IN-1, that has the unprecedented ability to target a unique cysteine residue located outside of the canonical kinase domain, providing an unanticipated means of achieving selectivity for CDK7 amongst the 20 known CDKs. Cancer cell line profiling indicates that a subset of cancer cell lines, including T-cell acute lymphoblastic leukemia (T-ALL), exhibit 100-fold greater sensitivity to CDK7-IN-1 over other tumor and normal cell lines. Genome-wide expression analysis in Jurkat T-ALL indicates that CDK7-IN-1 disproportionally affects RUNX1 as well as other components of the TAL1 transcriptional network and its targets, downregulating key regulators of transcription and apoptosis critical for the T-ALL state. These oncogenes are encoded by short-lived mRNA transcripts, are associated with super-enhancers, and exhibit a strong dependency on continuous transcription for sustained expression. Therefore, pharmacological modulation of CDK7 kinase activity may define a method for the identification and treatment of tumor types exhibiting extreme dependencies on transcription for maintenance of the oncogenic state. Jurkat, MM1S, Loucy, and HeLa (WT and Dox-inducible CDK7 mutant) cells were treated with various drugs including a covalent inhibitor of CDK7 (CDK7-IN-1), a reversible inhibitor of CDK7 (CDK7-IN-1), Flavopiridol, Actinomycin D, and DMSO controls. Replicates are annotated.
Project description:Cyclin dependent kinases activation and RNA polymerase II transcription are linked by the Cdk7 kinase that phosphorylates Cdks as a trimeric CAK complex, and serine 5 within the PolII C-terminal domain (CTD) as TFIIH bound CAK. However, the physiological importance of integrating these processes is not understood. Beside the Cdk7 ortholog Mcs6, fission yeast possesses a second CAK, Csk1. Both enzymes were proposed to act redundantly to activate Cdc2. Using an improved analogue sensitive Mcs6-as kinase, we show that Csk1 is not a relevant CAK for Cdc2. Further analyses revealed that Csk1 lacks a 20 amino acid sequence required for its budding yeast counterpart, Cak1, to bind Cdc2. Transcriptome profiling of the Mcs6-as mutant in the presence or absence of the budding yeast Cak1 kinase, in order to uncouple the CTD kinase and CAK activities of Mcs6, revealed an unanticipated role of the CAK branch in the transcriptional control of the cluster of genes implicated in ribosome biogenesis and cell growth. The analysis of a Cdc2 CAK site mutant confirmed these data. Our data show that the Cdk7 kinase modulates transcription through both its well-described RNA Polymerase II CTD kinase activity, but also through the Cdc2 activating kinase activity.
Project description:Triple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer that exhibits extremely high levels of genetic complexity and yet a relatively uniform transcriptional program. We postulate that TNBC might be highly dependent on uninterrupted transcription of a key set of genes within this gene expression program and might therefore be exceptionally sensitive to inhibitors of transcription. Utilizing a novel kinase inhibitor and CRISPR/Cas9-mediated gene editing, we show here that triple-negative but not ER/PR+ breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. TNBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An “Achilles cluster” of TNBC-specific genes are extremely sensitive to CDK7 inhibition and frequently associated with super-enhancers. We conclude that CDK7 mediates transcriptional addiction to a vital cluster of genes in TNBC and CDK7 inhibition may be useful therapy for this challenging cancer. Expression microarrays in H3K27ac in triple-negative breast cancer +/- treatment with covalent CDK7 inhibitor THZ1 treatment
Project description:Transcriptional co-acticvators inhibition is proving to be a powerful mean against cancer cells that shown a novel hallmarks named transcriptional addiction. This dependecy on co-activars activity lays on their presence in clusters of enhancer regulatory regions called Super-enhancers (SEs) that establish high level of expression of genes important for cancer phisiology such as oncogenes and master transcription factors of the cellular lineage of origin. Among these co-activators in SEs is the kinase CDK7 of the basal transcription factor TFIIH. Here, using a large panel of melanoma cell lines, we observed an overall dependency of melanoma cells in CDK7 activity by inhibiting its function through the drug THZ1. However, by chronically exposing melanoma cells to THZ1, they univocally become resistant, switching phenotype toward a mesenchymal-like state.
Project description:Basal-like breast cancer (BBC) is a highly aggressive form of breast cancer that exhibits extremely high levels of genetic complexity and yet a relatively uniform transcriptional program. We postulate that BBC might be highly dependent on uninterrupted transcription of a key set of genes within this gene expression program and might therefore be exceptionally sensitive to inhibitors of transcription. Utilizing a novel kinase inhibitor and CRISPR/Cas9-mediated gene editing, we show here that basal but not luminal breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. BBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An “Achilles cluster” of BBC-specific genes are extremely sensitive to CDK7 inhibition and frequently associated with super-enhancers. We conclude that CDK7 mediates transcriptional addiction to a vital cluster of genes in BBC and CDK7 inhibition may be useful therapy for this challenging cancer. ChIP-Seq for H3K27ac in basal-like breast cancer and luminal-like breast cancer cell lines