The tumor suppressor p53 is a transcription factor that coordinates the cellular response to DNA damage. Here we provide an integrated analysis of p53 genomic occupancy and p53-dependent gene regulation in the splenic B and non-B cell compartments of mice exposed to whole-body ionizing radiation, providing insight into general principles of p53 activity in vivo. In unstressed conditions, p53 bound few genomic targets; induction of p53 by ionizing radiation increased the number of p53 bound sites, leading to highly overlapping profiles in the different cell types. Comparison of these profiles with chromatin features in unstressed B cells revealed that, upon activation, p53 localized at active promoters, distal enhancers, and a smaller set of unmarked distal regions. At promoters, recognition of the canonical p53 motif as well as binding strength were associated with p53-dependent transcriptional activation, but not repression, indicating that the latter was most likely indirect. p53-activated targets constituted the core of a cell type-independent response, superimposed onto a cell type-specific program. Core response genes included most of the known p53-regulated genes, as well as many new ones. Our data represent a unique characterization of the p53-regulated response to ionizing radiation in vivo. Overall design: Total RNA profiling of gene expression in the splenic B and non-B cell compartments of wild-type and Trp53-/-mice exposed to whole-body ionizing radiation by Illumina sequencing
p53 transcriptional programs in B cells upon exposure to genotoxic stress in vivo: Computational analysis of next-generation sequencing data.
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Compensatory RNA polymerase 2 loading determines the efficacy and transcriptional selectivity of JQ1 in Myc-driven tumors.
Specimen part, Treatment
View SamplesWe here use B-cell tumors as a model to address the mechanism of action of JQ1, a widely used BET inhibitor.
Compensatory RNA polymerase 2 loading determines the efficacy and transcriptional selectivity of JQ1 in Myc-driven tumors.
Treatment
View SamplesThe tumor suppressor p53 is a transcription factor that controls the response to stress. Here, we dissected the transcriptional programs triggered upon restoration of p53 in Myc-driven lymphomas, based on the integrated analysis of p53 genomic occupancy and gene regulation. p53 binding sites were identified at promoters and enhancers, both characterized by the pre-existence of active chromatin marks. p53 recruitment at these sites was mainly mediated through protein-protein or protein-chromatin interactions and, only for a small fraction, through recognition of the 20 base-pair p53 consensus motif. At promoters, p53 binding to the consensus motif was associated with gene induction, but not repression, indicating that the latter was most likely indirect. p53 also targeted unmarked distal sites devoid of activation marks, at which binding was prevalently driven by recognition of the consensus motif. At all sites, our data highlighted a functional role for the canonical, unsplit consensus element, but did not provide evidence for p53 recruitment by split motifs. Altogether, our data highlight key features of genome recognition by p53 and provide unprecedented insight into the pathways associated with p53 re-activation and tumor regression. Overall design: Total RNA profiling of gene expression in Eµ-myc lymphomas following p53 restoration by Illumina sequencing
Genome-wide analysis of p53-regulated transcription in Myc-driven lymphomas.
Specimen part, Cell line, Subject
View SamplesThe Grainyhead family of transcription factors controls morphogenesis and differentiation of epithelial cell layers in multicellular organisms by regulating cell junction- and proliferation-related genes. Grainyhead-like 2 (Grhl2) is expressed in developing mouse lung epithelium and is required for normal lung organogenesis. The specific epithelial cells expressing Grhl2 and the genes regulated by Grhl2 in normal lungs are mostly unknown. In these studies, we identified the NK2 homeobox 1 transcription factor (Nkx2-1) as a direct transcriptional target of Grhl2. By binding and transcriptional assays, and by confocal microscopy we showed that these two transcription factors form a positive feed-back loop in vivo and in cell lines, and are co-expressed in lung bronchiolar and alveolar type II cells. The morphological changes observed in flattening lung alveolar type II cells in culture are associated with down-regulation of Grhl2 and Nkx2-1. Reduction of Grhl2 in lung epithelial cell lines results in lower expression levels of Nkx2-1 and of known Grhl2 target genes. By microarray analysis we identified that in addition to Cadherin1 and Claudin4, Grhl2 regulates other cell interaction genes such as semaphorins and their receptors, which also play a functional role in developing lung epithelium. Impaired collective cell migration observed in Grhl2 knockdown cell monolayers is associated with reduced expression of these genes and may contribute to the altered epithelial phenotype reported in Grhl2 mutant mice. Thus, Grhl2 functions at the nexus of a novel regulatory network, connecting lung epithelial cell identity, migration and cell-cell interactions.
The transcription factors Grainyhead-like 2 and NK2-homeobox 1 form a regulatory loop that coordinates lung epithelial cell morphogenesis and differentiation.
Cell line
View SamplesOver-expression of the Myc transcription factor causes its widespread interaction with regulatory domains in the genome, but leads to the up- and down-regulation of discrete sets of genes. The molecular determinants of these selective transcriptional responses remain elusive. Here, we present an integrated time-course analysis of transcription and mRNA dynamics following Myc activation in proliferating mouse fibroblasts, based on chromatin immunoprecipitation, metabolic labeling of newly synthesized RNA, extensive sequencing and mathematical modeling. Transcriptional activation correlated with the highest increases in Myc binding at promoters. Repression followed a reciprocal scenario, with the lowest gains in Myc binding. Altogether, the relative abundance (henceforth, “share”) of Myc at promoters was the strongest predictor of transcriptional responses in diverse cell types, predominating over Myc's association with the co-repressor Miz1. Myc activation elicited immediate loading of RNAPII at activated promoters, followed by increases in pause-release5, while repressed promoters showed opposite effects. Gains and losses in RNAPII loading were proportional to the changes in the Myc share, suggesting that repression by Myc may be largely indirect, owing - at least in part - to competition for limiting amounts of RNAPII. Secondary to the changes in RNAPII loading, the dynamics of elongation and pre-mRNA processing were also rapidly altered at Myc regulated genes, leading to the transient accumulation of partially or aberrantly processed mRNAs. Altogether, our results shed light on how over-expressed Myc alters the various phases of the RNAPII cycle and the resulting transcriptional response. Overall design: Time course profiling of 4sU-labeled and total RNA upon Myc activation in 3T9-MycER mouse fibroblasts
Integrative analysis of RNA polymerase II and transcriptional dynamics upon MYC activation.
Specimen part, Subject
View SamplesSingle-cell RNA-seq analysis of pre- and postnatal mouse endolymphatic sac demonstrates two types of differentiated cells distinguished by their mRNA expression signatures. Overall design: mRNA-seq profiles from 213 single cells from embryonic day 12.5, 16.5, postnatal day 5 and 30 mouse endolymphatic sac were analyzed
Molecular architecture underlying fluid absorption by the developing inner ear.
Specimen part, Cell line, Subject
View SamplesIntroduction: Though heavy alcohol drinking has been well characterized as causing a variety of injuries, recent epidemiological evidence in humans suggests moderate consumption may provide beneficial effects. For example, there exists a J- or U-shaped relationship between the level of alcohol intake and cardiovascular disease risk. We investigated the underlying mechanisms of these positive consequences by identifying which genes are responsive to moderate alcohol intake in the liver, the primary site for alcohol metabolism. Methods: Twelve female, inbred, alcohol-preferring (iP10a) rats were split equally between chronic water exposure and voluntary chronic ethanol exposure. Hepatic cholesterol and triglyceride levels were analyzed both histologically and biochemically. Hepatic transcriptomes were paired-end sequenced on the Illumina HiScanSQ system. Reads were analyzed and mapped using CLCbio Genomics Workbench 4.9. We confirmed altered expression of a subset of genes using TaqMan-based qRT-PCR. To quantify DNA methylation, we first digested DNA with methylation sensitive restriction enzymes and then performed qPCR using TaqMan assays surrounding the digest sites. Calculating ?Ct between a mock digest and digest determines the percent methylation in that locus. Results: Voluntary alcohol consumption in iP10a rats modeled moderate consumption in humans. These levels did not result in intrahepatic fat accumulation. Sequencing produced ~1.2 Gb of sequence per sample, and 65% of reads mapped uniquely. Using a FDR corrected p value of 0.05 we found 250 altered transcripts. Ontology analysis of genes with a fold change =1.3 identified many cholesterol synthesis genes and cytoskeleton subunit genes, all of which were down-regulated. Of the 28 genes reanalyzed by qRT-PCR, altered expression was confirmed in 24 genes including the majority of the cholesterol synthesis and cytoskeleton subunit genes. Lastly, we profiled methylation throughout the promoter and gene body of four genes elicited in the RNA-Seq experiment. We found that alcohol caused demethylation at all loci; however this loss happened in a site-specific, tightly regulated manner. Conclusion: Voluntary consumption in the iP10a animals models moderate consumption in humans, does not produce intrahepatic fat accumulation, and causes down-regulation of a majority of cholesterol synthesis genes. Moderate alcohol also results in a tightly-regulated demethylation effect. Our results explain, at least in part, the J- or U-shaped relationship between level of alcohol intake and cardiovascular disease risk. Overall design: We sequenced 12 female iP10a rat hepatic transcriptomes providing 6 biological replicates for water control and 6 for ethanol treatment.
A snapshot of the hepatic transcriptome: ad libitum alcohol intake suppresses expression of cholesterol synthesis genes in alcohol-preferring (P) rats.
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View SamplesZNF521 is a multiple zinc finger transcription factor previously identified because abundantly and selectively expressed in normal CD34+ hematopoietic stem and progenitor cells. From microarray datasets, aberrant expression of ZNF521 has been reported in both pediatric and adult acute myeloid leukemia (AML) patients with MLL gene rearrangements. However, a proper validation of microarray data is lacking, likewise ZNF521 contribution in MLL-rearranged AML is still uncertain. In this study, we show that ZNF521 is significantly upregulated in MLL translocated AML patients from a large pediatric cohort, regardless of the type of MLL translocations such as MLL-AF9, MLL-ENL, MLL-AF10 and MLL-AF6 fusion genes. Our in vitro functional studies demonstrate that ZNF521 play a critical role in the maintenance of the undifferentiated state of MLL-rearranged cells. Furthermore, analysis of the ZNF521 gene promoter region shows that ZNF521 is a direct downstream target of both MLL-AF9 and MLL-ENL fusion proteins. Gene expression profiling of MLL-AF9-rearranged THP-1 cells after depletion of ZNF521 reveals correlation with several expression signatures including stem cell-like and MLL fusion dependent programs. These data suggest that MLL fusion proteins activate ZNF521 expression to maintain the undifferentiated state and contribute to leukemogenesis.
ZNF521 sustains the differentiation block in MLL-rearranged acute myeloid leukemia.
Specimen part, Cell line
View SamplesMetastatic colonization involves cancer cell lodgment or adherence in the microvasculature and subsequent migration of those cells across the endothelium into a secondary organ site. To study this process further, we analyzed transendothelial migration of human PC-3 prostate cancer cells in vitro. We isolated a subpopulation of cells, TEM4-18, that crossed an endothelial barrier more efficiently, but surprisingly, were less invasive than parental PC-3 cells in other contexts in vitro. Importantly, TEM4-18 cells were more aggressive than PC-3 cells in a murine metastatic colonization model. Microarray and FACS analysis of these cells showed that the expression of many genes previously associated with leukocyte trafficking and cancer cell extravasation were either unchanged or down-regulated. TEM4-18 cells exhibited characteristic molecular markers of an epithelial-to-mesenchymal transition (EMT), including frank loss of E-cadherin expression and upregulation of the E-cadherin repressor ZEB1. Silencing ZEB1 in TEM4-18 cells resulted in increased E-cadherin and reduced transendothelial migration. TEM4-18 cells also express N-cadherin, which was found to be necessary, but not sufficient for increased transendothelial migration. Our results extend the role of EMT in metastasis to transendothelial migration and implicate ZEB1 and N-cadherin in this process in prostate cancer cells.
ZEB1 enhances transendothelial migration and represses the epithelial phenotype of prostate cancer cells.
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