Project description:Eukaryotic genomes are folded into three-dimensional (3D) hierarchical architectures consisting of multi-way chromatin contacts that are involved in complex gene regulation. High-throughput chromosome conformation capture (Hi-C), chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) , and methods similar to these two rely on pairwise ligation of fragments in proximity in a population of cells, thus fail to reveal multi-way chromatin interactions in single allele at single fragment resolution. To explore higher-order chromatin interaction genome-widely, a straightforward strategy is integrating multi-fragment ligates preparation with third-generation sequencing technology. To achieve this purpose, we developed a protocol of in situ high throughput multi-way contact long read Pore-C sequencing (in situ HiPore-C) We performed genome-wide multi-way contact profiling analysis using data obtained from in situ HiPore-C sequencing of GM12878 and K562 cell lines.
Project description:Packaging of DNA into chromatin regulates DNA accessibility and consequently all DNA-dependent processes. The nucleosome is the basic packaging unit of DNA forming arrays that are suggested, by biochemical studies, to fold hierarchically into ordered higher-order structures of chromatin. This organization has been recently questioned using microscopy techniques, proposing an irregular structure. To address the principles of chromatin organization, we applied an in situ differential MNase-seq strategy and analyzed in silico the results of complete and partial digestions of human chromatin. We investigated whether different levels of chromatin packaging exist in the cell. We assessed the accessibility of chromatin within distinct domains of kb to Mb genomic regions, performed statistical analyses and computer modelling. We found no difference in MNase accessibility, suggesting no difference in fiber folding between domains of euchromatin and heterochromatin or between other sequence and epigenomic features of chromatin. Thus, our data suggests the absence of differentially organized domains of higher-order structures of chromatin. Moreover, we identified only local structural changes, with individual hyper-accessible nucleosomes surrounding regulatory elements, such as enhancers and transcription start sites. The regulatory sites per se are occupied with structurally altered nucleosomes, exhibiting increased MNase sensitivity. Our findings provide biochemical evidence that supports an irregular model of large-scale chromatin organization.
Project description:The yeast Hsp70 chaperone Ssb interacts with ribosomes and nascent chains to co-translationally assist protein folding. Here, we present a proteome-wide analysis of Hsp70 function during translation, based on in vivo selective ribosome profiling, that reveals mechanistic principles coordinating translation with chaperone-assisted protein folding. Ssb binds most cytosolic, nuclear, and mitochondrial proteins and a subset of ER proteins, supporting its general chaperone function. Position-resolved analysis of Ssb engagement reveals compartment- and protein-specific nascent chain binding profiles that are coordinated by emergence of positively charged peptide stretches enriched in aromatic amino acids. Ssbs’ function is temporally coordinated by RAC but independent from NAC. Analysis of ribosome footprint densities along orfs reveals that ribosomes translate faster at times of Ssb binding. This is coordinated by biases in mRNA secondary structure, and codon usage as well as the action of Ssb, suggesting chaperones may allow higher protein synthesis rates by actively coordinating protein synthesis with co-translational folding.
Project description:Deciphering the rules of genome folding in the cell nucleus is essential in order to understand its functions. Recent Hi-C studies have revealed that the genome is partitioned into topologically associating domains (TADs), which demarcate functional epigenetic domains defined by combinations of specific chromatin marks. However, whether TADs are true physical units in each cell nucleus, or whether they reflect statistical frequencies of measured interactions within cell populations is unclear. Here, using a combination of Hi-C, 3D-Fluorescent In Situ Hybridization (3D-FISH), super-resolution microscopy and polymer modeling, we provide an integrative view of chromatin folding in Drosophila. We observed that repressed TADs form a succession of discrete nano-compartments, interspersed by less condensed active regions. Single-cell analysis revealed a consistent TAD-based physical compartmentalization of the chromatin fiber, with some degree of heterogeneity in intra-TAD conformations and in cis and trans inter-TAD contact events. These results indicate that TADs are fundamental 3D genome units that engage in dynamic higher-order inter-TAD connections. This domain-based architecture is likely to play a major role in regulatory transactions during DNA-dependent processes.
Project description:Deciphering the rules of genome folding in the cell nucleus is essential in order to understand its functions. Recent Hi-C studies have revealed that the genome is partitioned into topologically associating domains (TADs), which demarcate functional epigenetic domains defined by combinations of specific chromatin marks. However, whether TADs are true physical units in each cell nucleus, or whether they reflect statistical frequencies of measured interactions within cell populations is unclear. Here, using a combination of Hi-C, 3D-Fluorescent In Situ Hybridization (3D-FISH), super-resolution microscopy and polymer modeling, we provide an integrative view of chromatin folding in Drosophila. We observed that repressed TADs form a succession of discrete nano-compartments, interspersed by less condensed active regions. Single-cell analysis revealed a consistent TAD-based physical compartmentalization of the chromatin fiber, with some degree of heterogeneity in intra-TAD conformations and in cis and trans inter-TAD contact events. These results indicate that TADs are fundamental 3D genome units that engage in dynamic higher-order inter-TAD connections. This domain-based architecture is likely to play a major role in regulatory transactions during DNA-dependent processes.
Project description:Deciphering the rules of genome folding in the cell nucleus is essential in order to understand its functions. Recent Hi-C studies have revealed that the genome is partitioned into topologically associating domains (TADs), which demarcate functional epigenetic domains defined by combinations of specific chromatin marks. However, whether TADs are true physical units in each cell nucleus, or whether they reflect statistical frequencies of measured interactions within cell populations is unclear. Here, using a combination of Hi-C, 3D-Fluorescent In Situ Hybridization (3D-FISH), super-resolution microscopy and polymer modeling, we provide an integrative view of chromatin folding in Drosophila. We observed that repressed TADs form a succession of discrete nano-compartments, interspersed by less condensed active regions. Single-cell analysis revealed a consistent TAD-based physical compartmentalization of the chromatin fiber, with some degree of heterogeneity in intra-TAD conformations and in cis and trans inter-TAD contact events. These results indicate that TADs are fundamental 3D genome units that engage in dynamic higher-order inter-TAD connections. This domain-based architecture is likely to play a major role in regulatory transactions during DNA-dependent processes.
Project description:Here we describe the principles of 3D genome folding dynamics in vertebrates and show how lineage-specific patterns of genome reshuffling can result in different chromatin configurations. We (i) identified different patterns of chromosome folding across vertebrate species, (ii) reconstructed ancestral marsupial and afrotherian genomes analyzing whole-genome sequences of 10 species representative of the major therian phylogroups, (iii) detected lineage-specific chromosome rearrangements and (iv) identified the dynamics of the structural properties of genome reshuffling through therian evolution.