Tetrahymena thermophila macronucleus chromosomes originate from chromatin breakage sequence defined TAD-like structures in micronucleus chromosomes
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PROVIDER: PRJNA589668 | ENA |
REPOSITORIES: ENA
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Project description:The somatic macronucleus (MAC) and germline micronucleus (MIC) of Tetrahymena thermophila differ in chromosome numbers, sizes, functions, transcriptional activities, and cohesin complex location. However, the higher-order chromatin organization in T. thermophila which contains both cohesin free MAC and cohesin located MIC are largely unknown. Here, we examined the higher-order chromatin organization in the two distinct nuclei of T. thermophila using the Hi-C and HiChIP. Interestingly, we found that the crescent MIC possess specific chromosome interaction pattern. All the telomeres or centromeres on the five MIC chromosomes clustering together, respectively, which could help to identify the midpoints of centromeres in the MIC. We found the transcriptionally active MAC chromosomes lack A/B compartments, topologically associating domains (TADs) and chromatin loops. The transcriptionally inert MIC chromosomes also without A/B compartments and chromatin loops, but have TAD-like structures. The boundaries of the TAD-like structures in the MIC were highly consistent with the chromatin breakage sequence (CBS) sites, suggesting that each TAD-like structure of the MIC chromosomes develops into one MAC chromosome during MAC development during conjugation. Overall, we revealed the higher-order chromatin organization in the T. thermophila and found the chromatin structures might play important roles during the development of the MAC chromosomes.
2020-02-21 | GSE140429 | GEO
Project description:The somatic macronucleus (MAC) and germline micronucleus (MIC) of Tetrahymena thermophila differ in chromosome numbers, sizes, functions, transcriptional activities, and cohesin complex location. However, the higher-order chromatin organization in T. thermophila is still largely unknown. Here, we explored the higher-order chromatin organization in the two distinct nuclei of T. thermophila using the Hi-C and HiChIP methods. We found that the meiotic crescent MIC has a specific chromosome interaction pattern, with all the telomeres or centromeres on the five MIC chromosomes clustering together, respectively, which is also helpful to identify the midpoints of centromeres in the MIC. We revealed that the MAC chromosomes lack A/B compartments, topologically associating domains (TADs), and chromatin loops. The MIC chromosomes have TAD-like structures but not A/B compartments and chromatin loops. The boundaries of the TAD-like structures in the MIC are highly consistent with the chromatin breakage sequence (CBS) sites, suggesting that each TAD-like structure of the MIC chromosomes develops into one MAC chromosome during MAC development, which provides a mechanism of the formation of MAC chromosomes during conjugation. Overall, we demonstrated the distinct higher-order chromatin organization in the two nuclei of the T. thermophila and suggest that the higher-order chromatin structures may play important roles during the development of the MAC chromosomes.
| S-EPMC7111529 | biostudies-literature
Project description:Meiosis occurs in all sexually reproducing unicellular and multicellular eukaryotes. Bouquet formation is indispensible for homologous pairing or recombination during meiotic prophase I, but the regulatory mechanism of this process remain largely unknown. Cyclins regulate the precise meiosis progression by activating cyclin-dependent kinases. We therefore investigated the functional contribution of cyclin Cyc2p during bouquet (named crescent in Tetrahymena) formation in Tetrahymena thermophila. As a conjugation specific gene, CYC2 expression is significantly upregulated at 2-4 h after the initiation of conjugation and Cyc2p mainly localized in cytoplasm as well as weakly in the meiotic micronucleus (Mic). CYC2 knockout mutants failed to form elongated crescent structure and aborted meiotic development. Mic DNA double-strand breakage (DSB) decreased in ΔCYC2 cells as shown by γ-H2A.X staining, consistent with the finding that expression level of SPO11, DMC1, and RAD51 decreased in ΔCYC2 cells. However, ΔCYC2 cells failed to form crescent structure when artificial DSBs were induced, indicating that the inability to enter crescent phase was not completely due to the lack of DSBs. The localization of tubulin showed that impaired structure of nuclei and nuclear membrane may contribute to the blocked Mic elongation. This is further supported by the observation that expression levels of two microtubule associated kinesin genes, KIN11 and KIN141, were significantly downregulated in ΔCYC2 cells. Interestingly, scnRNA accumulation seemed intact in ΔCYC2 cells whereas the intensity of the heterochromatin marker H3K23me3 was abnormally increased. Together, these results showed that cyclin Cyc2p is required for micronuclear meiosis by controlling meiotic prophase chromosome breakage and the microtubule movement of nuclei in Tetrahymena.
2018-12-14 | GSE108064 | GEO
Project description:Genotype Environment interaction in shell breakage
| PRJEB52178 | ENA
Project description:Chromosome conformation capture (3C) technologies have identified topologically associating domains (TADs) and larger A/B compartments as two salient structural features of eukaryotic chromosomes. These structures are sculpted by the combined actions of transcription and structural maintenance of chromosomes (SMC) superfamily proteins. Bacterial chromosomes fold into TAD-like chromosomal interaction domains (CIDs) but do not display A/B compartment-type organization. Here, we reveal that chromosomes of Sulfolobus archaea are organized into CID-like topological domains in addition to the larger A/B compartment-type structures that we described recently. We uncover local rules governing the identity of the topological domains. We also identify long-range loop structures which provide evidence of a hub-like structure that colocalizes genes involved in ribosome biogenesis. In addition to providing high resolution description of archaeal chromosome architectures, our data provide evidence for multiple modes of organization in prokaryotic chromosomes and yield novel insight into the evolution of eukaryotic chromosome conformation.
2020-12-28 | GSE159537 | GEO
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:Three-dimensional genome structure plays an important role in gene regulation. Globally chromosomes are organized into active and inactive compartments, while at the gene level looping interactions connect promoters to regulatory elements. Topologically Associating Domains (TADs), typically several hundred kilobases in size form an intermediate level of organization. Major questions include how TADs are formed and what their relation is with looping interactions between genes and regulatory elements. Here we performed a focused 5C analysis of a 2.8 Mb region on chromosome 7 surrounding CFTR in a panel of cell types. We find that the same TAD boundaries are present in all cell types, indicating that TADs represent a universal chromosome architecture. Further, we find that these TAD boundaries are present irrespective of expression and looping of genes located between them. In contrast looping interactions between promoters and regulatory elements are cell-type specific and occur mostly within TADs. This is exemplified by the CFTR promoter that in different cell types interacts with distinct sets of distal cell type-specific regulatory elements that are all located within the same TAD. Finally, we find that long-range associations between loci located in different TADs are also detected but these display much lower interaction frequencies than looping interactions within TADs. Interestingly, interactions between TADs are also highly cell type-specific and often involve loci clustered around TAD boundaries. These data point to key roles of invariant TAD boundaries in constraining as well as mediating cell type-specific long-range interactions and gene regulation. We investigated a 2.8 Mb region on Chromosome 7 (hg18 chr7: 115797757-118405450) containing the ENCODE region ENm001 42. The 5C experiment was designed to interrogate looping interactions between HindIII fragments containing transcription start sites (TSSs) and any other HindIII restriction fragment (distal fragments) in the target region. Libraries were generated for five cell lines: Caco2, Calu3, Capan1, GM12878 and HepG2, with two biological replicates for each line. 5C probes were designed at HindIII restriction sites (AAGCTT) using 5C primer design tools previously developed and made publicly available online at our My5C website (http://my5C.umassmed.edu). Probes were designed based on the ENCODE manual region 1 (ENM001) design 25 with additional probes placed throughout the region when appropriate. We also added probes to extend the analysis to include a 700 Kb gene desert region located directly adjacent to ENM001. Probe settings were: U-BLAST, 3; S-BLAST, 100; 15-MER, 3,000; MIN_FSIZE, 250; MAX_FSIZE, 20,000; OPT_TM, 65; OPT_PSIZE, 40. We designed 74 reverse 5C probes, and 605 forward 5C probes.
2016-01-07 | E-GEOD-75634 | biostudies-arrayexpress
Project description:Detailed genomic contact maps have revealed that chromosomes are composed of developmentally stable topologically associated domains (TADs) and more flexible sub-TADs. These domains reside in active and inactive nuclear compartments, but cause and consequence of compartmentalization are largely unknown. Here, we combined lacO/lacR binding platforms with allele-specific 4C technologies to track their precise position in the three-dimensional genome upon recruitment of NANOG, SUV39H1 or EZH2. We observed locked genomic loci resistant to spatial repositioning and unlocked loci that could be repositioned to different nuclear sub-compartments with distinct chromatin signatures. Focal protein recruitment caused the entire sub- TAD, but not surrounding regions, to engage in new genomic contacts. Compartment switching was uncoupled from gene expression changes and enzymatically modifying histones per se was insufficient for repositioning. Collectively this suggests that transassociated factors determine three-dimensional compartmentalization independent of their cis-effect on local chromatin composition and activity. 4C-seq was performed on a range of viewpoints in 129/Sv;C57BL/6 embryonic stem cells carying a lacO array in chromosome 8 and 11.
2015-12-19 | E-GEOD-76174 | biostudies-arrayexpress
Project description:The genome is partitioned into Topologically Associating Domains (TADs). About half of the boundaries of these TADs exhibit transcriptional activity and are correlated with better TAD insulation. However, the association between these transcripts and TAD insulation, enhancer:promoter interactions and transcription of genes remains unknown. Here we investigate the functional roles of these bRNAs (boundary-RNA) in boundary insulation and consequent effects on enhancer-promoter interactions and TAD transcription genome-wide and more specifically on the disease relevant INK4a/ARF TAD. Using a series of CTCF site deletions and bRNA knockdown experiments at this TAD boundary, we show a direct association of CTCF with the bidirectional bRNAs where the loss of bRNA triggers the concomitant loss of: CTCF at the TAD boundary, its insulation, enhancer:promoter interactions and gene transcription within the targeted TAD. We used another series of enhancer deletions and CRISPRi on promoters within INK4a/ARF TAD to better understand the regulation and origins of bRNA itself. We observe that the enhancers interact with boundaries and positively regulate the bRNA transcription at TAD boundaries. In return, the bRNAs recruit/stabilize the CTCF even on weak motifs within these boundaries and supports CTCF binding in clusters, therefore enhancing TAD insulation. This favors the intra-TAD enhancer:promoter interactions and leads to robust gene transcription. Functionally, bRNAs are more stable than eRNAs and their knockdown exactly mimics the CTCF site deletion. Furthermore, transcribing boundaries exhibit high TAD transcription in TCGA tumour datasets. Together, these results show that active enhancers directly mediate better insulation of TADs by activating the transcription at TAD boundaries triggering CTCF clustering at the boundary which results in better insulation and favours robust intra-TAD enhancer:promoter interactions to activate the gene transcription.
2022-12-28 | GSE180659 | GEO
Project description:Topological associating domains (TADs) are self-interacting genomic units crucial for shaping gene regulation patterns. Despite their importance, the extent of their evolutionary conservation and its functional implications remain largely unknown. In this study, we generate Hi-C and ChIP-seq data and compare TAD organization across four primate and four rodent species, and characterize the genetic and epigenetic properties of TAD boundaries in correspondence to their evolutionary conservation. We find 14% of all human TAD boundaries to be shared among all eight species (ultraconserved), while 15% are human-specific. Ultraconserved TAD boundaries have stronger insulation strength, CTCF binding, and enrichment of older retrotransposons, compared to species-specific boundaries. CRISPR-Cas9 knockouts of two ultraconserved boundaries in mouse models leads to tissue-specific gene expression changes and morphological phenotypes. Deletion of a human-specific boundary near the autism-related AUTS2 gene results in upregulation of this gene in neurons. Overall, our study provides pertinent TAD boundary evolutionary conservation annotations, and showcase the functional importance of TAD evolution.
2023-10-20 | GSE197926 | GEO