Project description:We report the effects of CDK9 inhibition (AZD4573) on the epigenetic landscape in Diffuse Large B-cell Lymphoma (DLBCL). This study utilized the Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) to assess genome-wide chromatin accessibility in two DLBCL cell lines, OCI-LY3 and VAL, treated with AZD4573 (30 nM) at 0, 3, and 8 hours. We found that CDK9 inhibition led to gain and loss of accessible chromatin genome-wide, with enrichment of CTCF/BORIS motifs in decreased accesibility regions.
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.
Project description:Deregulation of the MYC transcription factor is a key driver in lymphomagenesis. MYC induces global changes in gene expression that contribute to cell growth, proliferation and oncogenesis by stimulating the activity of RNA polymerases. A key feature in its ability to stimulate RNA Pol II activity is recruitment of pTEFb, an elongation factor whose catalytic core comprises CDK9/cyclin T complexes. Hence, MYC expression and function may be susceptible to CDK9 inhibition. Non-specific inhibitors of multiple CDKs have shown promise in B-cell malignancies, where their pro-apoptotic effect has been attributed to a reduction in transcription and downmodulation of short lived pro-survival proteins (e.g., Mcl-1). However, they lack a defined mechanism of action. Here we selectively targeted CDK9 in a pre-clinical study in DLBCL.
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. ChIP-seq of Pol II in HeLa cells before or after i-CDk9 treatment
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.
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
Project description:Cyclin-dependent kinase 9 (CDK9) phosphorylates RNA polymerase II to promote productive transcription elongation and the phosphorylation also regulates recruitment of the splicing machinery. Here we show that acute CDK9 inhibition affects splicing of thousands of mRNAs. CDK9 inhibition impairs global splicing and there is no evidence for a coordinated response between alternative splicing and the overall transcriptome. Alternative splicing is feature of aggressive prostate cancer (CRPC) and enables generation of an anti-androgen resistant version of a ligand-independent androgen receptor, AR-v7. We show that CDK9 inhibition compromises splicing of the androgen receptor (AR) mRNA due to the faulty utilization of alternative 3’splice site and introduction of premature stop codon. Consequently, this defective splicing results in the loss of AR and AR-v7 expression in models of CRPC. We show that CDK9 expression increases as PC cells develop CRPC-phenotype both in vitro and also in patient samples.