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/EBPa, C/EBPß, 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. Moreover, chemical inhibition of BET bromodomains is found to suppress the functional output 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, which supports leukemia maintenance and is suppressed by BET bromodomain inhibition. Overall design: PolyA selected RNA-Seq for drug treated or shRNA-expressing MLL-AF9 transformed acute myeloid leukemia cells (RN2)
BET Bromodomain Inhibition Suppresses the Function of Hematopoietic Transcription Factors in Acute Myeloid Leukemia.
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View SamplesGenome occupancy profiling by high throughput sequencing Overall design: PolyA selected RNA-seq for shRNA-expressing MLL-AF9 transformed acute myeloid leukemia cells (RN2)
BET Bromodomain Inhibition Releases the Mediator Complex from Select cis-Regulatory Elements.
Specimen part, Cell line, Subject
View SamplesThe transcriptional activating and repressive functions performed by Trithorax and Polycomb group complexes, respectively, are critical for to maintain cellular fates in ontogeny and in cancer. Here we report that leukemias initiated by a Trithorax-related oncogene, MLL-AF9, depend upon the Polycomb Repressive Complex 2 (PRC2) to sustain a transformed cellular state. RNAi mediated suppression of PRC2 subunits is sufficient to inhibit proliferation of MLL-AF9 leukemias, with little impact on growth of non-transformed cells. This requirement is partly due to PRC2-mediated transcriptional repression of several anti-self-renewal regulators, including Cdkn2a. These results suggest that, unlike the classical antagonism generally observed between Polycomb and Trithorax group proteins during development, the activities of these two pathways can cooperate to promote myeloid neoplasia.
The Polycomb complex PRC2 supports aberrant self-renewal in a mouse model of MLL-AF9;Nras(G12D) acute myeloid leukemia.
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View SamplesG1E cells are a Gata-1 erythroid-committed cell line derived from targeted disruption of Gata-1 in embryonic stem cells. The ER4 subclone contains an inducible form of Gata-1 (Gata-1-ER, Gata-1 fused to the estradiol receptor ligand binding domain). We performed transcriptome analysis using this cell line. Estradiol was added to culture medium triggering synchronous and homogenous differentiation. At various time points, RNA was sampled and analyzed using the Affymetrix MG-U74Av2 platform. Three biological replicas (A,B, and C) were performed. The thirty hour time course corresponds to development from the late BFU-E stage through the orthochromatic erythroblast stage.
Global regulation of erythroid gene expression by transcription factor GATA-1.
No sample metadata fields
View SamplesMost mammalian transcription factors and cofactors occupy thousands of genomic sites and modulate the expression of large gene networks to implement their biological functions. In this study, we describe an exception to this paradigm. TRIM33 is identified here as a lineage dependency in B cell neoplasms and is shown to perform this essential function by associating with a single cis element. ChIP-seq analysis of TRIM33 in murine B cell leukemia revealed a preferential association with two lineage-specific enhancers that harbor an exceptional density of motifs recognized by the PU.1 transcription factor. TRIM33 is recruited to these elements by PU.1, yet acts to antagonize PU.1 function. One of the PU.1/TRIM33 co-occupied enhancers is upstream of the pro-apoptotic gene Bim, and deleting this enhancer renders TRIM33 dispensable for leukemia cell survival. These findings reveal an essential role for TRIM33 in preventing apoptosis in B lymphoblastic leukemia by interfering with enhancer-mediated Bim activation. Overall design: RNA-Seq for shRNAs targeting Trim33 expressing B-ALL
The transcriptional cofactor TRIM33 prevents apoptosis in B lymphoblastic leukemia by deactivating a single enhancer.
No sample metadata fields
View SamplesThe bromodomain and extraterminal (BET) protein BRD4 is a therapeutic target in acute myeloid leukemia (AML). Here, we demonstrate that the AML maintenance function of BRD4 requires its interaction with NSD3, which belongs to a subfamily of H3K36 methyltransferases. Unexpectedly, AML cells were found to only require a short isoform of NSD3 that lacks the methyltransferase domain. We show that NSD3-short is an adaptor protein that sustains leukemia by linking BRD4 to the CHD8 chromatin remodeler, by using a PWWP chromatin reader module, and by employing an acidic transactivation domain. Genetic targeting of NSD3 or CHD8 mimics the phenotypic and transcriptional effects of BRD4 inhibition. Furthermore, BRD4, NSD3, and CHD8 colocalize across the AML genome, and each is released from super-enhancer regions upon chemical inhibition of BET bromodomains. These findings suggest that BET inhibitors exert therapeutic effects in leukemia by evicting BRD4-NSD3-CHD8 complexes from chromatin to suppress transcription. Overall design: PolyA+ (illumine TruSeq)/not-so-random (NSR) primers selected RNA-Seq for shRNA/sgRNA-expressing MLL-AF9 transformed acute myeloid leukemia cells (RN2).
NSD3-Short Is an Adaptor Protein that Couples BRD4 to the CHD8 Chromatin Remodeler.
No sample metadata fields
View SamplesMissense FBXW7 mutations are prevalent in various tumors, including T-cell acute lymphoblastic leukemia (T-ALL). To study the effects of such lesions, we generated animals carrying regulatable Fbxw7 mutant alleles. We show here that these mutations specifically bolster cancer-initiating cell activity in collaboration with Notch1 oncogenes, but spare normal hematopoietic stem cell function. We were also able to show that FBXW7 mutations specifically affect the ubiquitylation and half-life of c-Myc protein, a key T-ALL oncogene. Using animals carrying c-Myc fusion alleles, we connected Fbxw7 function to c-Myc abundance and correlated c-Myc expression to leukemia-initiating activity.
The ubiquitin ligase FBXW7 modulates leukemia-initiating cell activity by regulating MYC stability.
Age, Specimen part
View SamplesCellular senescence is a homeostatic program associated with tumor suppression, wound healing, and certain age related pathologies. Senescent cells display a repressive chromatin configuration thought to stably silence proliferation-promoting genes, while at the same time activate an unusual form of immune surveillance involving a secretory program referred to as the senescence-associated secretory phenotype (SASP). Here we demonstrate that senescence also involves a global remodeling of the enhancer landscape with recruitment of the chromatin reader BRD4 to newly activated super-enhancers adjacent to key SASP genes. Transcriptional profiling and functional studies indicate that BRD4 is required for the SASP and downstream paracrine signaling. Consequently, BRD4 inhibition disrupts immune cell-mediated targeting and elimination of premalignant senescent cells in vitro and in vivo. Our results identify a critical role for BRD4-bound super-enhancers in senescence immune surveillance and in the proper execution of a tumor-suppressive program. Overall design: Analysis of RNA isolated from human fibroblasts (IMR90) in proliferating, quiescent or senescent (HrasV12) conditions upon knockdown of Brd4, p65, p53, p53/RB, p16/21 or Vehicle and JQ1 treatment
BRD4 Connects Enhancer Remodeling to Senescence Immune Surveillance.
No sample metadata fields
View SamplesThis SuperSeries is composed of the SubSeries listed below.
An integrated approach to dissecting oncogene addiction implicates a Myb-coordinated self-renewal program as essential for leukemia maintenance.
Specimen part, Treatment
View SamplesTo explore oncogene addiction programs in a genetically defined leukemia context we developed an AML mouse model driven by a conditional MLL-AF9 allele together with oncogenic Ras, which enabled us to examine the consequences of MLL-AF9 inhibition in established disease. In order to produce a tightly regulated system that was easy to monitor, we constructed two retroviral vectors containing dsRed-linked MLL-AF9 under control of a tetracycline response element promoter, and KrasG12D or NrasG12D linked to the Tet-off tet-transactivator, which activates TRE expression in a doxycycline repressible manner. Leukemias were generated by retroviral cotransduction of both vectors into hematopoietic stem and progenitor cells, which were transplanted into syngeneic mice. Cells harboring both constructs induced aggressive myelomonocytic leukemia. Five independent primary leukemia cell lines were established from bone marrow of terminal mice. Treatment of these lines with doxycycline rapidly turned off MLL-AF9 expression, and induced terminal myeloid differentiation and complete disease remission in vivo.
An integrated approach to dissecting oncogene addiction implicates a Myb-coordinated self-renewal program as essential for leukemia maintenance.
Specimen part, Treatment
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