Project description:Active regulatory elements in eukaryotes are typically characterized by an open, nucleosome-depleted chromatin structure; mapping areas of open chromatin has accordingly emerged as a widely used tool in the arsenal of modern functional genomics. However, existing approaches for profiling chromatin accessibility are limited by their reliance on DNA fragmentation and short read sequencing, which leaves them unable to provide information about the state of chromatin on larger scales or reveal coordination between the chromatin state of individual distal regulatory elements. To address these limitations, we have developed a method for profiling accessibility of individual chromatin fibers at multi-kilobase length scale (SMAC-seq, or Single-Molecule long-read Acessible Chromatin mapping sequencing assay), enabling the simultaneous, high-resolution, single-molecule assessment of the chromatin state of distal genomic elements. Our strategy is based on combining the preferential methylation of open chromatin regions by DNA methyltransferases (CpG and GpC 5-methylcytosine (5mC) and N6-methyladenosine (m6A) enzymes) and the ability of long-read single-molecule nanopore sequencing to directly read out the methylation state of individual DNA bases. Applying SMAC-seq to the budding yeast Saccharomyces cerevisiae, we demonstrate that aggregate SMAC-seq signals match bulk-level accessibility measurements, observe single-molecule protection footprints of nucleosomes and transcription factors, and quantify the correlation between the chromatin states of distal genomic elements
Project description:The cohesin complex is central to chromatin looping, but mechanisms by which these long-range chromatin interactions are formed and persist remain unclear. We demonstrate that interactions between a transcription factor and the cohesin loader NIPBL regulate enhancer-promoter looping and promote long-range gene regulation. Using mass-spectrometry, genome mapping, and single-molecule tracking methods, we demonstrate that NIPBL and cohesin regulate the dynamics and function of the glucocorticoid receptor (GR). Moreover, glucocorticoid treatment stabilizes NIPBL and cohesin interactions by promoting loop extrusion and chromatin looping. Patient-derived acute myeloid leukemia cells harboring cohesin mutations exhibit a reduced response to glucocorticoids (GCs), suggesting that the GR-NIPBL-cohesin interaction is defective in these patients, and they may be poor candidates for GC treatment.
Project description:Histone proteins have traditionally been thought to be restricted to eukaryotes and most archaea, with eukaryotic nucleosomal histones deriving from their archaeal ancestors. In contrast, bacteria lack histones as a rule. However, in recent years histone proteins have been identified in a few bacterial clades, in particular the phylum Bdellovibrionota, and these histones have been proposed to exhibit a range of divergent features compared to histones in archaea and eukaryotes. However, no experimental functional genomic studies of the properties of Bdellovibrionota chromatin have been carried out. In this work, we map the landscape of chromatin accessibility, active transcription and three-dimensional genome organization in a member of Bdellovibrionota (a Bacteriovorax strain). We find that Bacteriovorax chromatin is characterized by preferential accessibility around promoter regions, similar to what is observed in eukaryotes with compact genomes such as yeast, and also to some archaea. As in eukaryotes, chromatin accessibility positively correlates with gene expression. Mapping active transcription through single-strand DNA (ssDNA) profiling revealed that Bacteriovorax promoters exhibit very strong polymerase pausing, unlike in yeast, but similar to the state of mammalian and fly promoters. Finally, the Bacteriovorax genome exists in a three-dimensional (3D) conformation analogous to that of other bacteria without histones, organized by the parABS system and along the axis defined by replication origin and termination regions. These results provide a foundation for understanding the chromatin biology of the unique Bdellovibrionota bacteria and the deep evolution of chromatin organization across the tree of life.
Project description:Cis-regulatory elements coordinate the regulation of their targeted genes’ expression. However, the joint measurement of cis-regulatory elements’ activities and their interactions in spatial proximity is limited by the current sequencing approaches. We describe a method, NOMe-HiC, which simultaneously captures single nucleotide polymorphisms, DNA methylation, chromatin accessibility (GpC methyltransferase footprints), and chromosome conformation changes from the same DNA molecule, together with the transcriptome, in a single assay. NOMe-HiC shows high concordance with state-of-the-art mono-omic assays across different molecular measurements and reveals coordinated chromatin accessibility at distal genomic segments in spatial proximity and novel types of long-range allele-specific chromatin accessibility.
Project description:Cell-to-cell variation is a universal feature of life that impacts a wide range of biological phenomena, from developmental plasticity to tumor heterogeneity. While recent advances have improved our ability to document cellular phenotypic variation the fundamental mechanisms that generate variability from identical DNA sequences remain elusive. Here we reveal the landscape and principles of cellular DNA regulatory variation by developing a robust method for mapping the accessible genome of individual cells via assay of transposase accessible chromatin sequencing (ATAC-seq). Single-cell ATAC-seq (scATAC-seq) maps from hundreds of single-cells in aggregate closely resemble accessibility profiles from tens of millions of cells and provides insights into cell-to-cell variation. Accessibility variance is systematically associated with specific trans-factors and cis-elements, and we discover combinations of trans-factors associated with either induction or suppression of cell-to-cell variability. We further identify sets of trans-factors associated with cell-type specific accessibility variance across 6 cell types. Targeted perturbations of cell cycle or transcription factor signaling evoke stimulus-specific changes in this observed variability. The pattern of accessibility variation in cis across the genome recapitulates chromosome topological domains de novo, linking single-cell accessibility variation to three-dimensional genome organization. All together, single-cell analysis of DNA accessibility provides new insight into cellular variation of the “regulome.” Profiles of single cell epigenomes, assayed using scATAC-seq, across 8 cell types and 4 targeted cell manipulations. The complete data set contains a total of 1,632 assayed wells.
Project description:We report the application of single-molecule-based DNA sequencing technology for high-throughput profiling of long-range chromatin interactions in Sox2-deleted and wild type NSC, by improved ChIA-PET procedure (in situ ChIA-PET) with antiRNApolII antibodies. By obtaining sequences from chromatin immunoprecipitated DNA, we generated genome-wide maps of inter-molecular ligated DNA representing long-range interactions in chromatin.
Project description:Chromatin accessibility mapping by DNase-seq on whole embryo and FACS-isolated cell populations during Drosophila melanogaster embryogenesis at 2-4 hrs, 4-6 hrs, 6-8 hrs, 8-10 hrs and 10-12 hrs after egg-laying. Note that the two 8 bases long UMIs clipped from read1 and read2 are present in the FastQ file header (followed by the 8 bp long invariant sample barcode)