Project description:The liver X receptors (LXRs) are nuclear receptors that form permissive heterodimers with retinoid X receptor (RXR) and are important regulators of lipid metabolism in the liver. We have recently shown that RXR agonist-induced hypertriglyceridemia and hepatic steatosis in mice is dependent on LXR and correlates with an LXR-dependent hepatic induction of lipogenic genes. To further investigate the role of RXR and LXR in the regulation of hepatic gene expression, we have mapped the ligand-regulated genome-wide binding of these factors in mouse liver. We find that the RXR agonist bexarotene primarily increases the genomic binding of RXR, whereas the LXR agonist T0901317 greatly increases both LXR and RXR binding. Functional annotation of putative direct LXR target genes revealed a significant association with classical LXR-regulated pathways as well as PPAR signaling pathways, and subsequent ChIP-seq mapping of PPARα binding demonstrated binding of PPARα to 71-88% of the identified LXR:RXR binding sites. Sequence analysis of shared binding regions combined with sequential ChIP on selected sites indicate that LXR:RXR and PPARα:RXR bind to degenerate response elements in a mutually exclusive manner. Together our findings suggest extensive and unexpected cross-talk between hepatic LXR and PPARα at the level of binding to shared genomic sites LXR, RXR, PPARalpha and RNA Polymerase II ChIP-seq on livers from female C57BL/6 wild-type and/or LXRα/β-deficient mice (13 weeks of age, n=1) treated by oral gavage once daily for 14 days with the RXR agonist bexarotene (100 mg/kg body weight [mpk], in 1% carboxymethylcellulose), the LXR agonist T0901317 (T09, 30 mpk) or vehicle alone.
Project description:Introduction: Autoreactivity to histones is a pervasive feature of several human autoimmune disorders including systemic lupus erythematosus (SLE). Specific post-translational modifications (PTMs) of histones within neutrophil extracellular traps (NETs) may potentially drive the process by which tolerance to these chromatin-associated proteins is broken. We hypothesized that NETs and their unique histone PTMs might be capable of inducing autoantibodies that target histones. Methods: We developed a novel and efficient method for the in vitro production, visualization, and broad profiling of histone-PTMs of human and murine NETs. We also immunized Balb/c mice with murine NETs and profiled their sera on autoantigen and histone peptide microarrays for evidence of autoantibody production to their immunogen. Results: We confirmed specificity toward acetyl-modified histone H2B as well as to other histone PTMs in sera from patients with SLE known to have autoreactivity against histones. We observed enrichment for distinctive histone marks of transcriptionally silent DNA during NETosis triggered by diverse stimuli. However, NETs derived from human and murine sources did not harbor many of the PTMs toward which autoreactivity was observed in patients with SLE or in MRL/lpr mice. Further, while murine NETs were weak autoantigens in vivo, there was only partial overlap in the IgG and IgM autoantibody profiles induced by vaccination of mice with NETs and those seen in patients with SLE. Conclusions: Isolated in vivo exposure to NETs is insufficient to break tolerance and may involve additional factors that have yet to be identified. Serum samples from 20 systemic lupus erythematosis patients were run on the Human Epigenome Microarray Platform V1.0 (HEMP; a single-color platform), in order to profile their autoantibodies against a library of post-translationally modified histone peptides. These 20 samples were randomly selected from a larger cohort previously profiled (data not shown) on the Utz Lab Whole Protein Autoantigen Array V2.0 (a single-color platform), where 14 were histone-reactive and 6 were histone-nonreactive. Control sera from 9 healthy adults and a positive control comprising a mixture of autoimmune sera with defined reactivities, were also run on HEMP V1.0. Together, these samples comprise the data appearing in Figures 1 and S1 (IgG and IgM isotype reactivity profiles, respectively), identifying IgG reactivity to 9 peptides that significantly distinguish histone-reactive from -nonreactive sera among 96 peptides profiled. For data appearing in Figure 5, serum samples from a total of 6 Balb/c mice, consisting of two treatment groups, NETs (Neutrophil Extracellular Traps) and NETs + CRAMP (cathelicidin-related antimicrobial peptide) were collected monthly over a 3-month period, along with a zero time point. These samples were compared with a positive control consisting of serum collected from a MLR/lpr mice exhibiting lupus-like symptoms, and a negative control with no serum. The 0, 1 and 2 month time points were profiled on the Utz Lab Whole Protein Autoantigen Array V2.0 and are shown in Figure 5A-B, while the 1 and 3 month time points were profiled on HEMP V1.0 arrays and shown in Figure 5E. All samples were run once with no replicates.
Project description:ChIP on CHIP analysis were performed to analyse the direct involvement of Ino80 in the regulation of the phosphate responsive and nucleotide metabolism genes upon phosphate starvation: We immunoprecipitated Ino80-bound chromatin fragments after formaldehyde crosslinking from cells grown in minimal medium (EMM) or minimal medium lacking phosphate and purified, amplified and probed the Ino80-associated DNA using oligonucleotide tiling arrays.
Project description:Here we have used a combination of advanced proteomics and genomics approaches to investigate the extent and mechanisms of transcription factor cross-talk at genomic hotspots. We identify ~12,000 transcription factor hotspots in the early phase of adipogenesis, and we find evidence of both simultaneous and sequential binding of transcription factors at these regions. We demonstrate for the first time that hotspots are highly enriched in large super-enhancer regions and that these drive the early adipogenic reprogramming of gene expression. Our results indicate that cooperativity between transcription factors at the level of hotspots as well as super-enhancers is very important for enhancer activity and transcriptional reprogramming. Thus, hotspots and super-enhancers constitute important regulatory hubs integrating external stimuli on chromatin. Genome-wide profiling of transcription factor and co-factor binding, epigenomic marks, and gene expression in 3T3-L1 pre-adipocytes.
Project description:The conserved Nuclear Factor I (NFI) family of transcription factors is unique to animals and essential for mammalian development. The C. elegans genome encodes a single NFI family member, whereas vertebrate genomes encode four distinct NFI protein subtypes (A, B, C, and X). NFI-1 deficient worms exhibit abnormalities including reduced lifespan, defects in movement and pharyngeal pumping, and delayed egg-laying. To explore the functional basis of these phenotypes, we sought to comprehensively identify NFI-1 binding targets in C. elegans. We first established NFI-1 DNA-binding specificity using an in vitro DNA-selection strategy. Analysis yielded a consensus motif of TTGGCA(N3)TGCCAA, which occurs 586 times in the genome, a 100-fold higher frequency than expected. We next asked which sites were occupied by NFI-1 in vivo by performing chromatin immunoprecipitation of NFI-1 followed by microarray hybridization (ChIP-chip). Only 55 genomic locations were identified, an unexpectedly small target set. In vivo NFI-1 binding sites tend to be upstream of genes involved in core cellular processes such as chromatin remodeling, mRNA splicing, and translation. Remarkably, 67/80 (84%) of the C. briggsae homologs of the identified targets contain conserved NFI binding sites in their promoters. These experiments provide a foundation for understanding how NFI-1 is recruited to unexpectedly few in vivo sites to perform its developmental functions, despite a vast over-representation of its binding site. To our knowledge, this represents the first genome-wide location study of any transcription factor in C. elegans, and the first genome-wide analysis in any species of an NFI transcription factor. 4 biological replicates of NFI-1 ChIP-chip (including 1 dye-swap) were performed with 2 pre-immune Mock ChIP-chip controls from corresponding extracts.
Project description:The budding yeast genome is marked by 250-350 origins of DNA replication. These origins are bound by the origin recognition complex (ORC) throughout the cell cycle. ORC has known DNA binding sequence preferences which, though necessary for binding, are not sufficient to fully specify a genomic locus as being bound by ORC, indicating that the cell must use additional chromosomal cues to specify ORC binding sites and origins of replication. Using high-throughput sequencing to precisely locate both ORC binding sites and nucleosome locations genome-wide, we find that a nucleosome depleted region (NDR) and precisely positioned nucleosomes are a ubiquitous feature of yeast replication origins. The ARS consensus sequence (ACS) and adjacent sequences are sufficient to maintain the nucleosome-free properties of the NDR. We use a temperature sensitive ORC1 mutant to demonstrate that ORC is required to maintain precisely positioned nucleosomes at origins of replication. These findings demonstrate the importance of local nucleosome positioning at replication origins, and that chromatin organization is an important determinant of origin selection. Examination of nucleosome positioning in wild-type and orc1-161ts mutant S. cerevisiae at room temperature and heatshock temperatures. Examination of ORC binding locations by ChIP-seq. All reported coordinates are based on the SGD genome build released 12/16/2005.
Project description:The mammalian circadian clock is a molecular oscillator composed of a feedback loop that involves transcriptional activators CLOCK and BMAL1, and repressors Cryptochrome (CRY) and Period (PER). Here we show that a direct CLOCK-BMAL1 target gene, Gm129, is a novel regulator of the feedback loop. ChIP analysis revealed that the CLOCK:BMAL1:CRY1 complex strongly occupies the promoter region of Gm129. Both mRNA and protein levels of GM129 exhibit high amplitude circadian oscillations in mouse liver, and Gm129 gene encodes a nuclear-localized protein that directly interacts with BMAL1 and represses CLOCK:BMAL1 activity. In vitro and in vivo protein-DNA interaction results demonstrate that, like CRY1, GM129 functions as a repressor by binding to the CLOCK:BMAL1 complex on DNA. Although Gm129-/- or Cry1-/- Gm129-/- mice retain a robust circadian rhythm, the peaks of Nr1d1 and Dbp mRNAs in liver exhibit significant phase delay compared to control. Our results suggest that, in addition to CRYs and PERs, GM129 protein contributes to the transcriptional feedback loop by modulating CLOCK:BMAL1 activity as a transcriptional repressor. Examination of 3 transcriptional regulators in mouse liver
Project description:To assess the contribution to defenses against necrotrophic fungal pathogens that may be mediated by recognition of oligogalacturonides (OGs), cell wall fragments released by the activity of fungal polygalacturonases, we treated seedlings with OGs and assayed transcript levels 1 and 6 hours after addition of OGs to culture medium. For each sample, approximately 30 seedlings were grown in shallow liquid MS medium for 10 days. Plants were then treated with either 200 ug/ml OGs or, for control plants, an equal volume of water. Three replicate samples were assayed for each treatment.
Project description:The positioning of nucleosomes within the coding regions of eukaryotic genes is aligned with respect to transcriptional start sites. This organization is likely to influence many genetic processes, requiring access to the underlying DNA. Here we show that the combined action of Isw1 and Chd1 nucleosome spacing enzymes is required to maintain this organization. In the absence of these enzymes regular positioning of the majority of nucleosomes is lost. Exceptions include the region upstream of the promoter, the +1 nucleosome and a subset of locations distributed throughout coding regions where other factors are likely to be involved. These observations indicated that ATP-dependent remodeling enzymes are responsible for directing the positioning of the majority of nucleosomes within the Saccharomyces cerevisiae genome. Examination of nucleosome positioning in mutants of snf2-related enzymes Other data used in this study are provided in GEO Series GSE31301 and GSE31833.
Project description:We treated Jurkat cells for 48 hr with a sublethal dose of FK866 (5 nM) and DMSO (Mock, control treatment). RNA samples for microarrays derived from fractionated samples by sucrose gradient (sub-polysomes, polysomes), giving us the chance to perform an analysis among polysomal/subpolysomal distribution in treated or untreated cells and the possibility to identify the multi-level gene expression regulation effects of FK866. We are interested to find differentially expressed genes, in the early phase of cell response to FK866, and genes that account for a specific post-transcriptional regulation exerted by the cell in response to the drug. Keywords: polysomal profiling, translatome profiling, polysomal RNA, subpolysomal RNA, translational profiling, polysome profiling, post-transcriptional regulation, FK866, translational efficiency. Gene expression signals derived from the polysomal and subpolysomal RNA populations were compared by microarrays analysis to those obtained from total RNAs (derived from the sum of all the fractions in the polysomal gradient). Polysomal RNA, subpolysomal RNA and total RNA were isolated from Jurkat cells treated with FK866 5 nM or DMSO (mock, control treatment) for 48 hr. Cells lysates were collected from control cells (mock) and from treated cells (FK866). All experiments were run in biological quadruplicates.