Project description:We use a metabolic labeling strategy for directly measuring nucleosome turnover to determine the role of chromatin remodeler Chd1 on chromatin dynamics in mouse embryonic fibroblasts expressing with wildtype-Chd1 and dominant negative K510R-Chd1. We find that expression of K5 10R-Chd1 decreases nucleosome turnover at the promoter and increases turnover within the gene body. 10 Illumina sequencing samples and 4 Nimblegen array samples
Project description:Chromatin immunoprecipitation (ChIP) and its derivatives are the main techniques used to determine transcription factor binding sites. However, conventional ChIP with sequencing (ChIP-seq) has problems with poor resolution and newer techniques require significant experimental alterations and complex bioinformatics. Here we build upon our high-resolution crosslinking ChIP-seq (X-ChIP-seq) method and compare it to existing methodologies. By using micrococcal nuclease, which has both endo- and exo-nuclease activity to fragment the chromatin and thereby generate precise protein-DNA footprints, high-resolution X-ChIP-seq achieves single base pair resolution of transcription factor binding. A significant advantage of this protocol is the minimal alteration to the conventional ChIP-seq workflow and simple bioinformatic processing. Using High-resolution X-ChIP-seq we determined the genome-wide binding profile of various DNA binding proteins.
Project description:The TATA binding protein (TBP) is a transcription factor that binds specifically to a DNA sequence called the TATA box upstream of the transcription start site. To gain insight into the genes occupied by TBP, chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq) was performed to determine the genome-wide binding targets. DNA was enriched by chromatin immunoprecipitation (ChIP) and analyzed by Solexa sequencing. ChIP was performed using an antibody against TBP.
Project description:Multiple protein complexes and histone marks have been implicated and/or associated with gene repression in ES cells. To gain insights into repressive complexes present at repressed genes and their associated chromatin state, we profiled REST, MCAF1, Ring1b and H4K20me3 in mouse ES cells. DNA was enriched by chromatin immunoprecipitation (ChIP) and analyzed by Solexa sequencing. ChIP was performed using an antibody against REST, MCAF1, Ring1b and H4K20me3.
Project description:Sequence-specific DNA-binding proteins including transcription factors (TFs) are key determinants of gene regulation and chromatin architecture. Formaldehyde cross-linking and sonication followed by Chromatin ImmunoPrecipitation (X-ChIP) and sequencing is widely used for genome-wide profiling of protein binding, but is limited by low resolution and poor specificity and sensitivity. We have implemented a simple genome-wide ChIP protocol that starts with micrococcal nuclease-digested uncross-linked chromatin followed by affinity purification and paired-end sequencing without size-selection. The resulting ORGANIC (Occupied Regions of Genomes from Affinity-purified Naturally Isolated Chromatin) profiles of the budding yeast TFs Abf1 and Reb1 achieved near-perfect accuracy, in contrast to other profiling methods, which were much less sensitive and specific. Unlike profiles produced using X-ChIP methods such as ChIP-exo, ORGANIC profiles are not biased toward identifying sites in accessible chromatin and do not require input normalization. We also demonstrate the high specificity of our method when applied to larger genomes by profiling Drosophila GAGA Factor and Pipsqueak. Taken together, these results suggest that ORGANIC profiling outperforms current X-ChIP methodologies for genome-wide profiling of TF binding sites. Chromatin immunoprecipitation of micrococcal nuclease-digested native chromatin followed by paired-end sequencing (Occupied Regions of Genomes from Affinity-purified Naturally Isolated Chromatin 'ORGANIC' profiling) of DNA-binding proteins Abf1 and Reb1 from S. cerevisiae and GAGA-binding factor (GAF) and Pipsqueak (Psq) from D. melanogaster S2 cells; and, Sono-seq (paired-end sequencing of formaldehyde cross-linked and sonicated chromatin) of yeast nuclei. Reb1 ORGANIC profiling was performed at three different salt (NaCl) concentrations (80, 150, and 600 mM) and Abf1 ORGANIC profiling was done at two different salt concentrations (80 and 600 mM) to achieve varying levels of stringency. GAF and Psq ORGANIC profiles were determined at 80 mM salt. Two replicates each of Reb1 and Abf1 600 mM ORGANIC experiments, mixed Drosophila S2 cell and S. cerevisiae nuclei Reb1 ORGANIC experiments, yeast Sono-seq, and GAF and Psq ORGANIC experiments were performed. Each S. cerevisiae and mixed S2 cell/yeast ORGANIC profiling experiment included separately sequenced input chromatin and ChIP samples. Total of 24 samples.
Project description:Chromatin remodelers influence genetic processes by altering nucleosome occupancy, positioning, and composition. In vitro, yeast ISWI and CHD remodelers require > 20 bp of extranucleosomal DNA for remodeling, but linker DNA in S. cerevisiae averages < 20 bp. To resolve this paradox, we have mapped the genomic distributions of the yeast Isw1, Isw2, and Chd1 remodelers at base-pair resolution. Surprisingly, remodelers are highly enriched at promoter nucleosome depleted regions (5' NDRs), where they bind to regions of extended linker DNA. Remodelers are also enriched in the bodies of genes displaying high nucleosome turnover. We hypothesize that remodelers bind but do not act at 5' NDRs, remaining in physical proximity to gene bodies, where they act on regions of transient nucleosome depletion following transcriptional elongation. We have analyzed the dynamics of yeast ISWI and CHD chromatin remodeler genomic association at base-pair resolution using native chromatin immunoprecipitation followed by sequencing (N-ChIP-seq).
Project description:Post-translational modification of histones are coupled to transcription where certain modifications are indicative of an active or inactive region of the genome. Additionally, protein complexes can regulate the placement of nucleosomes across the genome and this influences the ability of DNA-binding proteins to interact with regions of the genome. The datasets presented here are ChIP-seq datasets for chromatin modifications associated with active or poised genes (H2Bub, H3K9,K14Ac and H3K4me3). Brg1 is a subunit of the SWI/SNF chromatin remodeling complex. An antibody specific to the chromatin modification or indicated factor was used to enrich for DNA fragments in murine embryonic stem cells. DNA was purified and prepared for Illumina/Solexa sequencing following their standard protocol.
Project description:The master transcription factors Oct4, Sox2 and Nanog bind enhancer elements and recruit the Mediator co-activator to activate much of the gene expression program of embryonic stem cells (ESCs). We report here that the ESC master transcription factors and Mediator form “super-enhancers” at most genes known to control the pluripotent state, including those encoding the master transcription factors themselves. These super-enhancers consist of extraordinarily large genomic domains occupied by exceptional amounts of Oct4, Sox2, Nanog, Klf4, Esrrb and Mediator. Super-enhancers stimulate considerably higher transcription than typical enhancers in vivo and in reporter vectors. Reduced levels of Oct4 or Mediator cause preferential loss of expression of super-enhancer-associated genes relative to other genes, suggesting how changes in gene expression programs might be accomplished during development. In other more differentiated cells, super-enhancers containing cell-type-specific master transcription factors are also found at genes that define cell identity. These results implicate super-enhancers in the control of mammalian cell identity and differentiation. ChIP-Seq and controls associated with Super-Enhancers in murine cell types
Project description:E4F1 is a ubiquitously expressed zinc-finger protein of the Gli-Kruppel family that was first identified, more than 30 years ago, as a cellular target of the adenoviral oncoprotein E1A13S (Ad type V), required for transcriptional regulation of adenoviral genes. In order to decipher E4F1 cellular target genes, we performed chromatin immunoprecipitation of endogenous E4F1 in primary and in p53KO, Ha-RasV12-transformed MEFs. Both input and immunoprecipitated DNA were exhaustively sequenced and mapped on the mouse genome (mm9). Peak detection has been achieved by combining two peak calling algorithms. Intersection of the two E4F1 peak lists on each cell line were considered as E4F1 chromatin bound regions. Genome-wide mapping of E4F1 binding in mouse embryonic fibroblasts.