BET bromodomain proteins function as master transcription elongation factors independent of CDK9 recruitment
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE79290 | GEO | 2017/09/18
SECONDARY ACCESSION(S): PRJNA315412
REPOSITORIES: GEO
Similar Datasets
Project description:Processive elongation of RNA Polymerase II from a proximal promoter paused state is a rate-limiting event in human gene control. A small number of regulatory factors influence transcription elongation on a global scale. Prior research using small-molecule BET bromodomain inhibitors, such as JQ1, linked BRD4 to context-specific elongation at a limited number of genes associated with massive enhancer regions. Here, the mechanistic characterization of an optimized chemical degrader of BET bromodomain proteins, dBET6, led to the unexpected identification of BET proteins as master regulators of global transcription elongation. In contrast to the selective effect of bromodomain inhibition on transcription, BET degradation prompts a collapse of global elongation that phenocopies CDK9 inhibition. Notably, BRD4 loss does not directly affect CDK9 localization. These studies, performed in translational models of T cell leukemia, establish a mechanism-based rationale for the development of BET bromodomain degradation as cancer therapy.
| S-EPMC5663500 | biostudies-literature
Project description:Cancer arises from the malignant interplay between oncogenic signaling and cell specification. Transcriptionally activated stem, growth and survival programs reshape an epigenomic identity defined by a transcriptional core regulatory circuitry. To study and disrupt oncogenic transcription, we first created inhibitors of BET bromodomains. Selective antagonism of oncogenic transcriptional signaling arises from bromodomain-specific activity. Recently, we innovated a strategy to induce selective and pronounced degradation of BET coactivator proteins via phthalimide conjugation for E3 ubiquitin ligase recruitment. Degraders of BET bromdomains (dBETs) exhibited superior efficacy to bromodomain inhibitors in cultivated leukemia cells, through unknown mechanisms. Here, we use chemically optimized small-molecule degronimids and kinetic measures of chromatin structure and function to unveil an unrecognized, essential role for BRD4 in the control of global productive transcriptional elongation. Rapid loss of BRD4 attenuates phosphorylation of the carboxy-terminal domain of RNA polymerase II, independent of genomewide recruitment of CDK9 to promoters, leading to a collapse of the transcriptional core regulatory circuitry. These mechanistic studies are performed in translational models of T-cell acute lymphoblastic leukemia, a disease emblematic for transcriptional addiction, to establish a rationale for human clinical investigation.
2017-09-18 | GSE79253 | GEO
Project description:Cancer arises from the malignant interplay between oncogenic signaling and cell specification. Transcriptionally activated stem, growth and survival programs reshape an epigenomic identity defined by a transcriptional core regulatory circuitry. To study and disrupt oncogenic transcription, we first created inhibitors of BET bromodomains. Selective antagonism of oncogenic transcriptional signaling arises from bromodomain-specific activity. Recently, we innovated a strategy to induce selective and pronounced degradation of BET coactivator proteins via phthalimide conjugation for E3 ubiquitin ligase recruitment. Degraders of BET bromdomains (dBETs) exhibited superior efficacy to bromodomain inhibitors in cultivated leukemia cells, through unknown mechanisms. Here, we use chemically optimized small-molecule degronimids and kinetic measures of chromatin structure and function to unveil an unrecognized, essential role for BRD4 in the control of global productive transcriptional elongation. Rapid loss of BRD4 attenuates phosphorylation of the carboxy-terminal domain of RNA polymerase II, independent of genomewide recruitment of CDK9 to promoters, leading to a collapse of the transcriptional core regulatory circuitry. These mechanistic studies are performed in translational models of T-cell acute lymphoblastic leukemia, a disease emblematic for transcriptional addiction, to establish a rationale for human clinical investigation.
2017-09-18 | GSE79288 | GEO
Project description:Cancer arises from the malignant interplay between oncogenic signaling and cell specification. Transcriptionally activated stem, growth and survival programs reshape an epigenomic identity defined by a transcriptional core regulatory circuitry. To study and disrupt oncogenic transcription, we first created inhibitors of BET bromodomains. Selective antagonism of oncogenic transcriptional signaling arises from bromodomain-specific activity. Recently, we innovated a strategy to induce selective and pronounced degradation of BET coactivator proteins via phthalimide conjugation for E3 ubiquitin ligase recruitment. Degraders of BET bromdomains (dBETs) exhibited superior efficacy to bromodomain inhibitors in cultivated leukemia cells, through unknown mechanisms. Here, we use chemically optimized small-molecule degronimids and kinetic measures of chromatin structure and function to unveil an unrecognized, essential role for BRD4 in the control of global productive transcriptional elongation. Rapid loss of BRD4 attenuates phosphorylation of the carboxy-terminal domain of RNA polymerase II, independent of genomewide recruitment of CDK9 to promoters, leading to a collapse of the transcriptional core regulatory circuitry. These mechanistic studies are performed in translational models of T-cell acute lymphoblastic leukemia, a disease emblematic for transcriptional addiction, to establish a rationale for human clinical investigation.
2017-09-18 | GSE79271 | GEO
Project description:BET bromodomain proteins function as master transcription elongation factors independent of CDK9 recruitment
| PRJNA315412 | ENA
Project description:BET bromodomain inhibitors block prostate cancer cell growth at least in part through c-Myc and androgen receptor (AR) suppression. However, little is known about other transcriptional regulators whose suppression contributes to BET bromodomain inhibitor anti-tumor activity. Moreover, the anti-tumor activity of BET bromodomain inhibition in AR-independent castration-resistant prostate cancers (CRPC), whose frequency is increasing, is also unknown. Herein, we demonstrate that BET bromodomain inhibition blocks growth of a diverse set of CRPC cell models, including those that are AR-independent or in which c-Myc is not suppressed. To identify transcriptional regulators whose suppression accounts for these effects, we treated multiple CRPC cell lines with the BET bromodomain inhibitor JQ1 and then performed RNA-sequencing followed by Master Regulator computational analysis. This approach identified several previously unappreciated transcriptional regulators that are highly expressed in CRPC and whose suppression, via both transcriptional or post-translational mechanisms, contributes to the anti-tumor activity of BET bromodomain inhibitors.
| S-EPMC6677126 | biostudies-literature
Project description:Developmental transitions are guided by master regulatory transcription factors. During adipogenesis, a transcriptional cascade culminates in the expression of PPARγ and C/EBPα, which orchestrate activation of the adipocyte gene expression program. However, the coactivators controlling PPARγ and C/EBPα expression are less well characterized. Here, we show the bromodomain-containing protein, BRD4, regulates transcription of PPARγ and C/EBPα. Analysis of BRD4 chromatin occupancy reveals that induction of adipogenesis in 3T3L1 fibroblasts provokes dynamic redistribution of BRD4 to de novo super-enhancers proximal to genes controlling adipocyte differentiation. Inhibition of the bromodomain and extraterminal domain (BET) family of bromodomain-containing proteins impedes BRD4 occupancy at these de novo enhancers and disrupts transcription of Pparg and Cebpa, thereby blocking adipogenesis. Furthermore, silencing of these BRD4-occupied distal regulatory elements at the Pparg locus by CRISPRi demonstrates a critical role for these enhancers in the control of Pparg gene expression and adipogenesis in 3T3L1s. Together, these data establish BET bromodomain proteins as time- and context-dependent coactivators of the adipocyte cell state transition.
| S-EPMC5834672 | biostudies-literature
Project description:There is increasing interest in inhibitors targeting BET (bromodomain and extra-terminal) proteins because of the association between this family of proteins and cancer progression. BET inhibitors were initially shown to have efficacy in hematologic malignancies; however, a number of studies have now shown that BET inhibitors can also block progression of non-hematologic malignancies. In this Review, we summarize the efficacy of BET inhibitors in select solid tumors; evaluate the role of BET proteins in mediating resistance to current targeted therapies; and consider potential toxicities of BET inhibitors. We also evaluate recently characterized mechanisms of resistance to BET inhibitors; summarize ongoing clinical trials with these inhibitors; and discuss potential future roles of BET inhibitors in patients with solid tumors.
| S-EPMC5288238 | biostudies-literature
Project description:Developmental transitions are guided by master regulatory transcription factors. During adipogenesis, a transcriptional cascade culminates in expression of PPARg and C/EBPa, which orchestrate activation of the adipocyte gene expression program. However, the coactivators controlling PPARg and C/EBPa expression are less well characterized. Here we show the bromodomain-containing protein, BRD4, regulates transcription of PPARg and C/EBPa. Analysis of BRD4 chromatin occupancy reveals that induction of adipogenesis in 3T3L1 fibroblasts provokes dynamic redistribution of BRD4 to de novo super enhancers proximal to genes controlling adipocyte differentiation. BET bromodomain inhibition impedes BRD4 occupancy at these de novo enhancers and disrupts transcription of Pparg and Cebpa, thereby blocking adipogenesis. Furthermore, silencing of these BRD4-occupied distal regulatory elements at the Pparg locus by CRISPRi demonstrates a critical role for these enhancers in the control of Pparg gene expression and adipogenesis in 3T3L1s. Together, these data establish BET bromodomain proteins as time- and context-dependent coactivators of the adipocyte cell state transition.
2018-03-07 | GSE109940 | GEO
Project description:The bromodomain and extraterminal (BET) protein BRD4 is a validated drug target in leukemia, yet its regulatory function in this disease is not well understood. Here, we show that BRD4 chromatin occupancy in acute myeloid leukemia closely correlates with the hematopoietic transcription factors (TFs) PU.1, FLI1, ERG, C/EBP?, C/EBP?, and MYB at nucleosome-depleted enhancer and promoter regions. We provide evidence that these TFs, in conjunction with the lysine acetyltransferase activity of p300/CBP, facilitate BRD4 recruitment to their occupied sites to promote transcriptional activation. Chemical inhibition of BET bromodomains was found to suppress the functional output of each hematopoietic TF, thereby interfering with essential lineage-specific transcriptional circuits in this disease. These findings reveal a chromatin-based signaling cascade comprised of hematopoietic TFs, p300/CBP, and BRD4 that supports leukemia maintenance and is suppressed by BET bromodomain inhibition.
| S-EPMC4475489 | biostudies-literature