ABSTRACT: 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:We aimed to determine the binding sites of the putative transcriptional regulator PafBC under DNA damage stress induced by mitomycin C or under oxidative stress induced by hydrogen peroxide. Therefore, we chose a ChIP-seq approach, crosslinking cells before PafBC-DNA complexes were immunoprecipitated with a PafBC-specific antibody.
Project description:Sequencing of the 3’ end of poly(A)+ RNA identifies cleavage and polyadenylation sites (pAs) and measures transcript expression. We previously developed a method, 3’ region extraction and deep sequencing (3’READS), to address mispriming issues that often plague 3’ end sequencing. Here we report a new version, named 3’READS+, which has vastly improved accuracy and sensitivity. Using a special locked nucleic acid oligo to capture poly(A)+ RNA and to remove bulk of the poly(A) tail, 3’READS+ generates RNA fragments with an optimal number of terminal As that balance data quality and detection of genuine pAs. With improved RNA ligation steps for efficiency, the method shows much higher sensitivity (over two orders of magnitude) compared to the previous version. Using 3’READS+, we have uncovered a sizable fraction of previously overlooked pAs located next to or within a stretch of adenylate residues in human genes, and more accurately assessed the frequency of alternative cleavage and polyadenylation (APA) in HeLa cells (~50%). 3’READS+ will be a useful tool to accurately study APA and to analyze gene expression by 3’ end counting, especially when the amount of input total RNA is limited. Nine 3'READS+ libraries were made with different amounts (100 ng, 200 ng, 400 ng, 1000 ng, 5000 ng, 15000 ng) of input Hela RNA.
Project description:Wild-type mouse embryonic stem cells are compared with mutants for components of PRC2 including Ezh2-/-, Eed-/-, and Jarid2-/- cells. Chromatin modifications, Gene expression, Pol-II, small-RNA sequencing, and DNA methylation are compared for both cell types. To study genomic and epigentic control of PRC2 in mESCs, we designed gene expression analysis (RNA-Seq and small RNA-Seq), combining with ChIP-Seq analysis of several factors and histone marks from wild-type and distinct PRC2 mutants including wild-type, Ezh2-/-, Eed-/-, and Jarid2-/-.
Project description:Embryonic stem cell (ESC) pluripotency is governed by a gene regulatory network centred on the transcription factors Oct4 and Nanog. ESCs fluctuate between states of high and low Nanog expression that direct efficient or inefficient self-renewal. To date, robust self-renewing ESC states have only been attained by chemical inhibition of signalling pathways or enforced transgene expression. Here we show that ESCs expressing a reduced range of Oct4 concentrations, typified by Oct4 heterozygous ESCs exhibit stable robust pluripotency. Despite this reduced Oct4 concentration range, this state is characterised by increased genome-wide binding of Oct4, particularly at pluripotency-associated enhancers, homogeneous expression of pluripotency transcription factors, enhanced self-renewal efficiency and delayed differentiation kinetics. In this state, ESCs exhibit increased wnt expression, enhanced LIF-sensitivity, non-responsiveness to FGF signalling and can clonally maintain pluripotency without BMP but remain dependent upon LIF. Robust pluripotency is destabilised either by alteration of the Oct4 level or by removal of LIF. Our findings suggest that robust pluripotency originates from cells with a reduced Oct4 protein concentration and that the wild-type Oct4 range enables effective differentiation.
Project description:Under continuous, glucose-limited conditions, budding yeast exhibit robust metabolic cycles associated with major oscillations of gene expression and metabolic state. However, how such fluctuations might be coordinately linked to changes in chromatin status is less well understood. Here, we examine the correlated genome-wide transcription and chromatin states across the yeast metabolic cycle (YMC) at unprecedented temporal resolution, revealing a "just in time supply chain" by which specific cellular processes such as ribosome biogenesis are coordinated in time with remarkable precision. We identify distinct chromatin and splicing patterns associated with different gene categories and determine the relative timing of chromatin modifications to maximal transcription. Additionally, we interrogate chromatin modifier occupancy and observe subtly distinct spatial and temporal patterns compared to the modifications themselves. Furthermore, we identify multiple lysine mutants in H3 or H4 tails that disrupt metabolic cycling, supporting a potentially cooperative role of histone modifications in the YMC. 16 time points RNA-seq and ChIP-seq of 8 histone marks over one metabolic cycle, 14 time points ChIP-seq of 3 chromatin modifiers over one metabolic cycle
Project description:We mapped the genome-wide binding of the flagellar regulators FlhD, FlhC, and FliA in FLAG-tagged derivatives of E. coli K-12 MG1655 using ChIP coupled with deep sequencing (ChIP-seq). We identify new binding sites for each factor.
Project description:By a robust unbiased ChIP-seq approach, we demonstrated that CRISPR/Cas9 had crRNA-specific off-target binding activities in human genome. However, most of those binding off-targets could not be efficiently cleaved both in vivo and in vitro which suggested the cleavage off-target activity of CRISPR/Cas9 in human genome is very limited. We provided a valuable tool to further investigate the molecular mechanism of CRISPR/Cas9 and to optimize its in vivo targeting sgRNA binding sites were identified with ChipSeq by using GFP antibody (there are 2 replicates for egfa-t1 sgRNA,emx1 sgRNA and control without sgRNA in Hek293T cells, one egfa-t1 sgRNA,emx1 sgRNA and control without sgRNA in HeLaS3 cells)