Gene expression following CDK9 silencing
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE21751 | GEO | 2010/05/09
SECONDARY ACCESSION(S): PRJNA127341
REPOSITORIES: GEO
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Project description:Cyclin-Dependent Kinase 9 (CDK9) as part of the PTEFb complex promotes transcriptional elongation by promoting RNAPII pause release. We now report that, paradoxically, CDK9 is also essential for maintaining gene silencing at heterochromatic loci. Through a live cell screen, we discovered that CDK9 inhibition reactivates epigenetically silenced genes in cancer, leading to restored tumor suppressor gene expression and cell differentiation, along with activation of endogenous retrovirus (ERV) genes. CDK9 inhibition dephosphorylates the SWI/SNF protein SMARCA4 and represses HP1α expression, both of which contribute to gene reactivation. Based on gene activation, we developed the highly selective and potent CDK9 inhibitor MC180295 (IC50 =5.1nM) that has broad anti-cancer activity in-vitro and is effective in in-vivo cancer models. Additionally, CDK9 inhibition sensitizes with the immune checkpoint inhibitor α-PD-1 in vivo, making it an excellent target for epigenetic therapy of cancer.
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Project description:CDK9 is the kinase subunit of P-TEFb that enables RNA polymerase (Pol) II to transit from promoter-proximal pausing to productive elongation. Although considerable interest exists in CDK9 as a therapeutic target, little progress has been made due to the lack of highly selective inhibitors. Here, we describe the development of i-CDK9 as such an inhibitor that potently suppresses CDK9 phosphorylation of substrates and causes genome-wide Pol II pausing. While most genes experience reduced expression, MYC and other primary response genes increase expression upon sustained i-CDK9 treatment. Essential for this increase, the bromodomain protein BRD4 captures P-TEFb from 7SK snRNP to deliver to target genes and also enhances CDK9’s activity and resistance to inhibition. Because the i-CDK9-induced MYC expression and binding to P-TEFb compensate for P-TEFb’s loss of activity, only the simultaneous inhibition of CDK9 and MYC can efficiently induce growth arrest and apoptosis of cancer cells, suggesting the potential of a combinatorial treatment strategy. We used microarrays to examine the global impact on gene expression by imhibiting CDK9 at different time durations. HeLa cell lines treated with CDK9 inhibitor at different time points
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Project description:Cyclin-dependent kinase 9 (CDK9) plays a critical role in transcription initiation and is essential for maintaining gene silencing at heterochromatic loci. Inhibition of CDK9 increases sensitivity to immunotherapy, but the underlying mechanism remains unclear. We now report that RNF20 stabilizes LSD1 via K29-mediated ubiquitination, which is dependent on CDK9-mediated phosphorylation. This CDK9- and RNF20-dependent LSD1 stabilization is necessary for the demethylation of histone H3K4, then subsequent repression of endogenous retrovirus (ERVs), and an interferon response, leading to epigenetic immunosuppression. Moreover, we found that loss of RNF20 sensitizes cancer cells to the immune checkpoint inhibitor anti-PD-1 in vivo, and that this effect can be rescued by the expression of ectopic LSD1. Our findings are supported by the observation that RNF20 levels correlate with LSD1 levels in human breast cancer specimens. This study sheds light on the role of RNF20 in CDK9-dependent LSD1 stabilization, which is crucial for epigenetic silencing and immunosuppression. Our findings explore the potential importance of targeting the CDK9-RNF20-LSD1 axis in the development of new cancer therapies.
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Project description:We report the effects of CDK9 inhibition (AZD4573) on the epigenetic landscape in Diffuse Large B-cell Lymphoma (DLBCL). This study utilized chromatin immunoprecipitation with massively parallel DNA sequencing (ChIP-seq) to assess genome-wide post-translational histone modifications (H3K27ac and H3K4me3) and DNA occupancy of transcriptional proteins (RNAPII and BRD4) in two DLBCL cell lines, OCI-LY3 and VAL, treated with the CDK9 inhibitor AZD4573 (30 nM). Cells were treated for 0, 3 and 8 hours prior to harvest. After 8-hour exposure, drug was washed out and cells were harvested after 24 hours. We found that CDK9 inhibition led to an increase in RNAPII promoter proximal pausing, and increase in BRD4 enrichment on the promoter, and a decrease in promoter H3K4me3. Treatment induced reprograming of the super-enhancer landscape including loss of super-enhancers next to genes in oncogenic pathways.
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