Co-location of chromatin loop anchors with the gene transcription machinery in maize.
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ABSTRACT:
ORGANISM(S): Zea mays
PROVIDER: GSE161294 | GEO | 2020/11/12
REPOSITORIES: GEO
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Project description:BackgroundThree-dimensional chromatin loop structures connect regulatory elements to their target genes in regions known as anchors. In complex plant genomes, such as maize, it has been proposed that loops span heterochromatic regions marked by higher repeat content, but little is known on their spatial organization and genome-wide occurrence in relation to transcriptional activity.ResultsHere, ultra-deep Hi-C sequencing of maize B73 leaf tissue was combined with gene expression and open chromatin sequencing for chromatin loop discovery and correlation with hierarchical topologically-associating domains (TADs) and transcriptional activity. A majority of all anchors are shared between multiple loops from previous public maize high-resolution interactome datasets, suggesting a highly dynamic environment, with a conserved set of anchors involved in multiple interaction networks. Chromatin loop interiors are marked by higher repeat contents than the anchors flanking them. A small fraction of high-resolution interaction anchors, fully embedded in larger chromatin loops, co-locate with active genes and putative protein-binding sites. Combinatorial analyses indicate that all anchors studied here co-locate with at least 81.5% of expressed genes and 74% of open chromatin regions. Approximately 38% of all Hi-C chromatin loops are fully embedded within hierarchical TAD-like domains, while the remaining ones share anchors with domain boundaries or with distinct domains. Those various loop types exhibit specific patterns of overlap for open chromatin regions and expressed genes, but no apparent pattern of gene expression. In addition, up to 63% of all unique variants derived from a prior public maize eQTL dataset overlap with Hi-C loop anchors. Anchor annotation suggests that < 7% of all loops detected here are potentially devoid of any genes or regulatory elements. The overall organization of chromatin loop anchors in the maize genome suggest a loop modeling system hypothesized to resemble phase separation of repeat-rich regions.ConclusionsSets of conserved chromatin loop anchors mapping to hierarchical domains contains core structural components of the gene expression machinery in maize. The data presented here will be a useful reference to further investigate their function in regard to the formation of transcriptional complexes and the regulation of transcriptional activity in the maize genome.
| S-EPMC7789236 | biostudies-literature
Project description:DNA replication occurs through an intricately regulated series of molecular events and is fundamental for genome stability. It is currently unknown how the location of replication origins is determined in the human genome. Here, we dissect the role for topologically associating domains (TADs), subTADs, and loops in the positioning of replication initiation zones (IZs). We stratify TADs/subTADs by the presence of corner-dots indicative of loops and the orientation of CTCF motifs. We find that high-efficiency, early replicating IZs localize to boundaries between adjacent corner-dot TADs anchored by high-density arrays of divergently and convergently-oriented CTCF motifs. By contrast, low-efficiency IZs localize to weak boundaries devoid of CTCF and corner-dots. Upon ablation of cohesin-mediated loop extrusion in G1, high-efficiency IZs become diffuse and de-localized specifically at boundaries with complex CTCF motif orientation. Moreover, G1 knock-down of the cohesin unloading factor WAPL results in gained long-range loops and narrowed localization of IZs at the same boundaries. Finally, targeted deletion or insertion of specific boundaries causes local replication timing shifts consistent with loss and gain of IZs, respectively. Our data support a model in which cohesin-mediated loop extrusion and stalling at a subset of genetically-encoded TAD/subTAD boundaries is an essential determinant of the precise location of replication initiation in human S phase.
2021-12-05 | GSE190117 | GEO
Project description:The depiction of maize chromatin architecture using Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq) provides great opportunities to investigate cis-regulatory elements, which is crucial for crop improvement. We demonstrate a streamlined ATAC-seq protocol for maize in which nuclei purification can be achieved without cell sorting, and using only a standard bench-top centrifuge. Our protocol, coupled with the bioinformatic analysis, provides a precise and efficient assessment of the maize chromatin landscape.
2024-01-10 | GSE252638 | GEO
Project description:FKBP5 is a long glucocorticoid-inducible gene implicated in psychiatric disorders. To investigate the complexities of chromatin interaction frequencies at the FKBP5 topologically associated domain (TAD), we deployed fifteen one-to-all chromatin capture viewpoints near gene promoters, enhancers, introns, and CTCF-loop anchors. This revealed a ‘one-TAD-one-gene’ structure encompassing the FKBP5 promoter and its enhancers. The FKBP5 promoter and its two glucocorticoid-stimulated enhancers roam the entire TAD while displaying subtle cell type-specific interactomes. The FKBP5 TAD consists of two nested CTCF loops that are coordinated by one CTCF site beyond the FKBP5 polyadenylation site and another in its 8th intron, 61 kb further. Loop extension correlates with transcription increases through the intronic CTCF site. This is efficiently compensated for, since the short loop is restored even under high transcription regimes. The boundaries of the FKBP5 TAD consist of divergent CTCF sites, harbor multiple smaller genes and are resilient to glucocorticoid stimulation. Interestingly, both FKBP5 TAD boundaries harbor H3K27me3-marked heterochromatin blocks that may reinforce them. We propose that cis-acting genetic and epigenetic polymorphisms underlying FKBP5 expression variation are likely to reside within a 240 kb region that consists of the FKBP5 TAD, its left sub-TAD, and both its boundaries.
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Project description:Chromatin organization and cell cycle are tightly intertwined in eukaryotes, but the underlying mechanisms remain unclear. We investigated how the retinoblastoma protein (RB), a key cell cycle regulator, influences chromatin architecture. Chromosome conformation capture assays reveal that RB loss increases the number and size of cohesin-dependent loops and strengthens topologically associating domains (TADs). RB shows extensive colocalization with cohesin in the human genome, and it impacts cohesin’s distribution on chromatin. Active RB evicted cohesin from RB-bound TAD boundaries, repressed insulator activity, and enhanced the expression of non-E2F target genes that are important for cell adhesion. We conclude that RB has a central role in the interplay between cell cycle and chromatin organization. This role safeguards chromatin architecture and controls transcription.
2024-11-01 | E-MTAB-13566 | biostudies-arrayexpress
Project description:Cohesin-mediated loop anchors confine the location of human replication origins
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Project description:Genome organization is driven by forces affecting transcriptional state, but the relationship between transcription and genome architecture remains unclear. Here, we identified the Drosophila transcription factor Motif 1 Binding Protein (M1BP) in physical association with the gypsy chromatin insulator core complex, including the universal insulator protein CP190. M1BP is required for enhancer-blocking and barrier activities of the gypsy insulator as well as its proper nuclear localization. Genome-wide, M1BP specifically colocalizes with CP190 at Motif 1-containing promoters, which are enriched at topologically associating domain (TAD) borders. M1BP facilitates CP190 chromatin binding at many shared sites and vice versa. Both factors promote Motif 1-dependent gene expression and transcription near TAD borders genome-wide. Finally, loss of M1BP reduces chromatin accessibility and increases both inter- and intra-TAD local genome compaction. Our results reveal physical and functional interaction between CP190 and M1BP to activate transcription at TAD borders and mediate chromatin insulator-dependent genome organization.
2021-06-07 | PXD026497 | Pride
Project description:Epigenomics and transcriptomics data from high-throughput sequencing techniques such as RNA-seq and ChIP-seq have been successfully applied in predicting gene transcript expression. However, the locations of chromatin loops in the genome identified by techniques such as Chromatin Interaction Analysis with Paired End Tag sequencing (ChIA-PET) have never been used for prediction tasks. Here, we developed machine learning models to investigate if ChIA-PET could contribute to transcript and exon usage prediction. In doing so, we used a large set of transcription factors as well as ChIA-PET data. We developed different Gradient Boosting Trees models according to the different tasks with the integrated datasets from three cell lines, including GM12878, HeLaS3 and K562. We validated the models via 10-fold cross validation, chromosome-split validation and cross-cell validation. Our results show that both transcript and splicing-derived exon usage can be effectively predicted with at least 0.7512 and 0.7459 of accuracy, respectively, on all cell lines from all kinds of validations. Examining the predictive features, we found that RNA Polymerase II ChIA-PET was one of the most important features in both transcript and exon usage prediction, suggesting that chromatin loop anchors are predictive of both transcript and exon usage.
| S-EPMC8575016 | biostudies-literature
Project description:Maize (Zea mays) is one of the most important crop in the world. Better understanding the maize chromatin architecture points to novel approaches to improve crop yield. Here, we describe the first ATAC-seq protocol to assess the maize genome. Fresh leaf tissue was gently chopped by a blade to release intact nuclei which later were fractionated using Percoll-sucrose gradient. The isolated nuclei were treated with a transposase that fragments and tags the genome; these fragments were subjected to two rounds of PCR to generate the ATAC-seq library. In the first round of PCR, these fragments were amplified with 5 cycles and sequencing barcodes were added. A fraction of the first PCR product was subjected to qPCR to determine the optimal amplification cycle number in the second round of PCR. The library quality can be assessed by a Bioanalyzer prior to sequencing. The distinct bands indicated good quality. After sequencing, the computational analysis of fragment size distribution may show patterns of periodicity that is a characteristic to ATAC-seq libraries. In our preliminary analysis, we found that 85% percent of the identified regions deviate from closed regions previously identified by MNase-seq, suggesting that the ATAC-seq library preparation procedure described here is effective in identifying open chromatin regions of the maize genome.
2019-01-23 | GSE120491 | GEO
Project description:Additional to GSE1807 A comparative analysis, by expression profiling of maize, was performed to identify novel components in the mechanisms of maize responses to UV-B. Five high-altitude landraces grown from 2,000 to 3,400 m naturally receive higher UV-B fluence than plants at lower altitudes and similar latitudes. These high-altitude landraces were compared directly with a low-altitude line and with literature reports for other temperate maize lines. A microarray analysis demonstrated that among the UV-B responsive transcripts, several types of gene implicated in chromatin remodeling are differentially expressed before and after UV-B treatment in high-altitude lines. RNAi transgenic plants with lower expression of four such chromatin-associated genes exhibited hypersensitivity to UV-B by measurements of leaf arching, increased leaf chlorosis and necrosis, and altered UV-B regulation of selected genes. These results collectively suggest that genes involved in chromatin remodeling are crucial for UV-B acclimation and that some high-altitude lines exhibit adaptations to this challenge.
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