Project description:The response regulator RpaA is required for control of genome-wide gene expression by the cyanobacterial circadian clock. RpaA is predicted to be a DNA binding protein based on sequence homology, but prior studies have been unable to detect binding in vitro or in vivo to a small panel of promoters. We used ChIP-Seq to determine whether RpaA associates with DNA in vivo, and if so, with what dynamics. We find that RpaA binds to over 100 location in the genome in a circadian manner, with strongest binding occuring around subjective dusk. Analysis of these binding sites shows that RpaA directly regulates the expression of clock components to generate feedback on the core oscillator, and also regulates expression of a small set of circadian effectors that in turn orchestrate global expression rhythms. Crosslinked samples were acquired every four hours from a turbidostatic wild-type (AMC408) cultures in constant light (LL) following entrainment with two light-dark (LD) cycles. As a negative control, we acquired samples similarly from an ΔrpaA culture. Chromatin immunoprecipitation was performed on each sample from wht wild-type and from a pool of all samples from the ΔrpaA culture. Libraries were prepared from the ChIP samples and sequenced with Illumina technology. For the wild-type, biological replicate samples were acquired at times of maximum and minimum RpaA binding.
Project description:ChIP-seq analysis was used to identify B. dermatitidis genes bound by the GATA transcription factor encoded by SREB during growth as yeast at 37oC SREB was engineered to contain an in-frame 3x-hemagglutinin (HA) epitope tag at the C-terminus. The SREB-3xHA construct was under control of its native promoter and contained the 3-untranslated region. Using Agrobacterium tumefaciens, B. dermatitidis ATCC 26199 was transformed with the SREB-3xHA construct (referred to a SREB-3xHA strain in this document). The SREB-3xHA construct was functional because retransformation of SREBΔ with the construct complented the null mutant. Chromatin was extracted and sheared from ATCC 26199 and SREB-3xHA yeast grown in liquid Histoplasma macrophage medium (HMM) containing 10 μM iron sulfate (FeSO4) at 37oC. ATCC 26199 was the untagged control strain.
Project description:Genomic enhancers regulate spatio-temporal gene expression by recruiting specific combinations of transcription factors (TFs). When TFs are bound to active regulatory regions, they displace canonical nucleosomes, making these regions biochemically detectable as nucleosome-depleted regions or accessible/open chromatin. Here we ask whether open chromatin profiling can be used to identify the entire repertoire of active promoters and enhancers underlying tissue-specific gene expression during normal development and oncogenesis in vivo. To this end, we first compare two different approaches to detect open chromatin in vivo using the Drosophila eye primordium as a model system: FAIRE-seq, based on physical separation of open versus closed chromatin; and ATAC-seq, based on preferential integration of a transposon into open chromatin. We find that both methods reproducibly capture the tissue-specific chromatin activity of regulatory regions, including promoters, enhancers, and insulators. Using both techniques, we screened for regulatory regions that become ectopically active during Ras-dependent oncogenesis, and identified 3778 regions that become (over-)activated during tumor development. Next, we applied motif discovery to search for candidate transcription factors that could bind these regions and identified AP-1 and Stat92E as key regulators. We validated the importance of Stat92E in the development of the tumors by introducing a loss of function Stat92E mutant, which was sufficient to rescue the tumor phenotype. Additionally we tested if the predicted Stat92E responsive regulatory regions are genuine, using ectopic induction of JAK/STAT signaling in developing eye discs, and observed that similar chromatin changes indeed occurred. Finally, we determine that these are functionally significant regulatory changes, as nearby target genes are up- or down-regulated. In conclusion, we show that FAIRE-seq and ATAC-seq based open chromatin profiling, combined with motif discovery, is a straightforward approach to identify functional genomic regulatory regions, master regulators, and gene regulatory networks controlling complex in vivo processes. FAIRE-Seq in Drosophila wild type eye-antennal imaginal discs (2 wt strains); ATAC-Seq in Drosophila wild type eye-antennal imaginal discs (3 wt strains) ; FAIRE-Seq in Drosophila Ras/Scrib induced eye disc tumors (1 early and 1 late); ATAC-Seq in Drosophila Ras/Scrib induced eye disc tumors (1 early and 1 late); ATAC-Seq in Drosophila eye discs with Unpaired over-expression (2 biological replicates); CTCF ChIP-seq in Drosophila eye discs; ChIP-seq input in Drosophila eye discs
Project description:modENCODE_submission_5124 This submission comes from a modENCODE project of Gary Karpen. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We aim to determine the locations of 125 chromosomal proteins across the Drosophila melanogaster genome. The proteins under study are involved in basic chromosomal functions such as DNA replication, gene expression, gene silencing, and inheritance. We will perform Chromatin ImmunoPrecipitation (ChIP) using the Illumina NGS platform. We will initially assay localizations using chromatin from three cell lines and two embryonic stages, and will then extend the analysis of a subset of proteins to four additional animal tissues/stages For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Strain: Oregon-R(official name : Oregon-R-modENCODE genotype : wild type ); Developmental Stage: Mixed Adult; Genotype: wild type; EXPERIMENTAL FACTORS: Strain Oregon-R(official name : Oregon-R-modENCODE genotype : wild type ); tissue (organism part) ; Antibody RNA Pol II (abcam) (target is PolII); Developmental Stage Mixed Adult
Project description:modENCODE_submission_3247 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We will precisely identify sequence elements that direct DNA replication by using chromatin immunoprecipitation of known replication initiation complexes. These experiments will be conducted in multiple cell types and developmental tissues. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Developmental Stage: Mixed Embryos 0-24h; EXPERIMENTAL FACTORS: Developmental Stage Mixed Embryos 0-24h; Antibody (target is dORC2); read length (read_length 36)
Project description:The DNA damage response network modulates a wide array of signaling pathways, including DNA repair, cell cycle checkpoints, apoptotic pathways and numerous stress signals. The ATM protein kinase, functionally missing in patients with the human genetic disorder ataxia-telangiectasia (A-T), is a master regulator of this network when the inducing DNA lesions are double strand breaks. The ATM gene is also frequently mutated in sporadic cancers of lymphoid origin. Here, we applied a functional genomics approach that combines gene expression profiling and computational promoter analysis to obtain global dissection of the transcriptional response to ionizing radiation (IR) in murine lymphoid tissue. Cluster analysis revealed six major expression patterns in the data. Prominent among them was a gene cluster that contained dozens of genes whose response to irradiation was Atm-dependent. Computational analysis identified significant enrichment of the binding site signatures of the transcription factors NF-kB and p53 among promoters of these genes, pointing to the major role of these two transcription factors in mediating the Atm-dependent transcriptional response in the irradiated lymphoid tissue. Examination of the response showed that pro- and anti-apoptotic signals were simultaneously induced, with the pro-apoptotic pathway mediated by p53, and the pro-survival pathway by NF-kB. These findings further elucidate the molecular network induced by IR and have implications for cancer management as they suggest that a combined treatment that restores the p53-mediated apoptotic arm while blocking the NF-kB-mediated pro-survival arm could be most successful in increasing the radiosensitivity of lymphoid tumors.
Project description:Although splicing occurs in most multi-exon genes, the generation of distinct isoforms through the alternate use of mutually exclusive exons is less prevalent. As exon-switching events have the potential to give rise to isoforms with different cellular functions, we have explored the role of the muscle-specific (Mef2Da2) and ubiquitously expressed (Mef2Da1) isoforms of the transcription factor Mef2D in myogenesis. Here we show that both isoforms of Mef2D bind a largely overlapping subset of genomic loci, yet only the muscle-specific Mef2Da2 isoform can activate the late myogenic gene expression program. This differential ability to activate transcription is modulated by PKA signaling where Mef2Da1 is efficiently phosphorylated by the kinase to enhance its association with repressive HDAC-deacetylase complexes. In contrast, alternate exon usage in Mef2Da2 renders the protein resistant to PKA phosphorylation, allowing it to interact with transcriptionally permissive Ash2L-trithorax complex. Our findings support a model wherein alternative exon usage allows Mef2D to transition from a repressor to activator in a myogenic environment rich in PKA activity. Thus we have identified a novel paradigm in which a ubiquitously expressed transcription factor has evolved to undergo tissue-specific alternative exon usage to permit the proper temporal activation of a gene expression program during differentiation. ChIP-Seq profiling of Mef2Da1 and Mef2Da2 isoforms generated by alternate splicing
Project description:Epithelial cells possess remarkable plasticity, having the ability to become mesenchymal cells through alterations in adhesion and motility (epithelial-to-mesenchymal transition or EMT). Recent studies suggest that EMT endows differentiated epithelial cells with stem cell traits, posing the interesting question of how epithelial plasticity is properly restricted to ensure epithelial differentiation during tissue morphogenesis. Here we identify zinc-finger transcription factor Ovol2 as a key suppressor of EMT of mammary epithelial cells. Epithelia-specific deletion of Ovol2 completely arrests mammary ductal morphogenesis, and depletes epithelial stem/progenitor cell reservoirs. Further, Ovol2-deficient epithelial cells undergo EMT in vivo to become non-epithelial cell types, and that Ovol2 directly represses key EMT inducers such as Zeb1 and regulates stem/progenitor cell responsiveness to TGF-beta. We also provide evidence for a suppressive role of Ovol2 in breast cancer progression. Our findings underscore the critical importance of exquisitely regulating epithelial plasticity to balance stemness with epithelial differentiation in development and cancer. We report ChIPseq data illustrating Ovol2 genome-wide targets in mouse mammary epithelial cells, suggesting that Ovol2 regulates a plethora of genes associated with the EMT process. Immunoprecipitated samples from HC11 mouse mammary epithelial cells with antibodies against Ovol2 and control IgG respectively were used for ChIP-seq experiments.
Project description:ChIP-seq of mouse embryonic fibroblast-adipose like cell line 3T3-L1 to identify binding sites of NCoR1 and SMRT following induction of differentiation, and RNA Pol-II after SMRT knock down
Project description:During cell division, transcription factors (TFs) are removed from chromatin twice, during DNA synthesis, and during condensation of chromosomes. How TFs can efficiently find their sites following these stages has been unclear. Here, we have analyzed the binding pattern of expressed TFs in human colorectal cancer cells. We find that binding of TFs is highly clustered, and that the clusters are enriched in binding motifs for several major TF classes. Strikingly, almost all clusters are formed around cohesin, and loss of cohesin decreases both DNA accessibility and binding of TFs to clusters. We show that cohesin remains bound in S phase, holding the nascent sister chromatids together at the TF cluster sites. Furthermore, cohesin remains bound to the cluster sites when TFs are evicted in early M-phase. These results suggest that cohesin binding functions as a cellular memory that promotes re- stablishment of TF clusters after DNA replication and chromatin condensation. Examination of TF binding by ChIP-seq in LoVo CRC cell-lines.