Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Genetic Evidence for Asymmetric Blocking of Higher-Order Chromatin Structure by CTCF/Cohesin

ABSTRACT: The architectural protein CTCF binds to mammalian insulators genome wide with directionality and recruits cohesin to mediate oriented long-distance chromatin loops. In many cases, CTCF-binding sites (CBSs) are associated with distal enhancers and target promoters. It is generally thought that CTCF binding results in spatial contacts between distal enhancers and target promoters leading to activation of specific promoters. However, how CTCF orchestrates higher-order chromatin organization to regulate gene expression is not fully understood. Here we used CRISPR DNA-fragment editing to investigate the roles of CTCF in chromatin organization of the clustered protocadherin (Pcdh) genes, which is an ideal model system with repertoires of CBSs in variable promoters and super-enhancers. We found that the CBSs at chromatin domain boundary and even single CBSs could determine the orientation of long-distance chromatin looping. In addition, deletion or inversion of large regions containing tandem CBS arrays in mice demonstrated asymmetric influences on chromatin looping between super-enhancers and target promoters. These genetic data have important implications on the assembly mechanisms of higher-order chromatin structures.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE135967 | GEO | 2019/09/15

REPOSITORIES: GEO

ACCESS DATA

Json Xml

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

CRISPR Inversion of CTCF Sites Alters Genome Topology and Enhancer/Promoter Function

Project description:CTCF/cohesin play a central role in insulator function and higher-order chromatin organization of mammalian genomes. Recent studies identified a correlation between the orientation of CTCF-binding sites (CBSs) and chromatin loops. To test the functional significance of this observation, we combined CRISPR/Cas9-based genomic-DNA-fragment editing with chromosome-conformation-capture experiments to show that the location and relative orientations of CBSs determine the specificity of long-range chromatin looping in mammalian genomes, using protocadherin (Pcdh) and β-globin as model genes. Inversion of CBS elements within the Pcdh enhancer reconfigures the topology of chromatin loops between the distal enhancer and target promoters, and alters gene-expression patterns. Thus, although enhancers can function in an orientation-independent manner in reporter assays, in the native chromosome context the orientation of at least some enhancers carrying CBSs can determine both the architecture of topological chromatin domains and enhancer/promoter specificity. The findings reveal how 3D chromosome architecture can be encoded by genome sequence.

2015-08-13 | GSE71275 | GEO

Low affinity CTCF binding drives transcriptional regulation whereas high affinity binding encompasses architectural functions.

Project description:This SuperSeries is composed of the SubSeries listed below. CTCF is a DNA-binding protein which plays critical roles in chromatin structure organization and transcriptional regulation; however, little is known about the functional determinants of different CTCF binding sites (CBS). Using a conditional mouse model, we have identified one set of CBSs that are lost upon CTCF depletion (lost CBSs) and another set that persists (retained CBSs). Retained CBSs are more similar to the consensus CTCF binding sequence and usually span tandem CTCF peaks. Lost CBSs are enriched at enhancers and promoters and associate with active chromatin marks and higher transcriptional activity. In contrast, retained CBSs are enriched at TAD and loop boundaries. Integration of ChIP-seq and RNA-seq data has revealed that retained CBSs are located at the boundaries between distinct chromatin states, acting as chromatin barriers. Our results provide evidence that transient, lost CBSs are involved in transcriptional regulation, whereas retained CBSs are critical for establishing higher-order chromatin architecture.

2023-02-10 | GSE207640 | GEO

Building regulatory landscapes reveals that an enhancer can recruit cohesin to create contact domains, engage CTCF sites and activate distant genes

Project description:Developmental gene expression is often controlled by distal regulatory DNA elements called enhancers. Distant enhancer action is restricted to structural chromosomal domains that are flanked by CTCF-associated boundaries and formed through cohesin chromatin loop extrusion. To better understand how enhancers, genes and CTCF boundaries together form structural domains and control expression, we used a bottom-up approach, building series of active regulatory landscapes in inactive chromatin. We demonstrate here that gene transcription levels and activity over time reduce with increased enhancer distance. The enhancer recruits cohesin to stimulate domain formation and engage flanking CTCF sites in loop formation. It requires cohesin exclusively for the activation of distant genes, not of proximal genes, with nearby CTCF boundaries supporting efficient long-range enhancer action. Our work supports a dual activity model for enhancers: its classic role to stimulate transcription initiation and elongation from target gene promoters and a role to recruit cohesin for the creation of chromosomal domains, the engagement of CTCF sites in chromatin looping, and the activation of distal target genes.

2022-04-08 | GSE180566 | GEO

Molecular Mechanism of Directional CTCF Recognition of a Diverse Range of Genomic Sites

Project description:CTCF, a conserved 3D genome architecture protein, determines proper genome-wide chromatin looping interactions through directional binding to specific sequence elements of four modules within numerous CTCF-binding sites (CBSs) by its 11 zinc fingers (ZFs). Here, we report the crystal structures of four human CTCF-CBS complexes of the protocadherin (Pcdh) clusters, and show that directional CTCF binding to cognate CBSs of the Pcdh enhancers and promoters is achieved through inserting its ZF3, ZFs 4-7, and ZFs 9-11 into the major groove along CBSs, resulting in a sequence-specific recognition of module 4, modules 2-3, and module 1, respectively, with ZF8 as a spacer element for variable distances between modules 1 and 2. In addition, the base-contact with the asymmetric “A” in the central position of modules 2-3, is essential for directional recognition of the CBSs with symmetric core sequences and lack of module 1. Furthermore, CTCF tolerates base changes at specific positions within the degenerated CBS sequences, permitting genome-wide CTCF binding to a diverse range of CBSs. Together, these complex structures provide important insights into the molecular mechanisms for the directionality, diversity, flexibility, dynamics, and conservation of multivalent CTCF binding to its cognate sites across the entire human genome

2017-10-30 | GSE103651 | GEO

An ectopic CTCF binding element disturbs VÎ´ usage at the mouse Tcra-Tcrd locus by regulating contact between VÎ´ and DÎ´ gene segments

Project description:Chromatin looping mediated by the CCCTC binding factor CTCF regulates V(D)J recombination at antigen receptor loci. CTCF-mediated looping can influence recombination signal sequence accessibility by regulating enhancer activation of germline promoters. CTCF-mediated looping has also been shown to limit directional tracking of the RAG recombinase along chromatin, and to regulate through-space interactions between recombination signal sequences, independent of the RAG recombinase. However, in all prior instances in which CTCF-mediated looping was shown to influence V(D)J recombination, it was not possible to fully resolve the relative contributions to the V(D)J recombination phenotype of changes in accessibility, RAG-tracking, and RAG-independent long-distance interactions. Here, to assess mechanisms by which CTCF-mediated looping can impact V(D)J recombination, we introduced an ectopic CTCF binding element (CBE) immediately downstream of EÎ´ in the murine Tcra-Tcrd locus. The ectopic CBE impaired inversional rearrangement of Trdv5 in the absence of measurable effects on Trdv5 transcription and chromatin accessibility. Moreover, although the ectopic CBE limited directional RAG tracking from the Tcrd recombination center, such tracking cannot account for Trdv5-to-Trdd2 inversional rearrangement. Rather, the defect in Trdv5 rearrangement could only be attributed to a reconfigured chromatin loop organization that limited RAG-independent through-space interactions between the Trdv5 and Trdd2 RSSs. We conclude that CTCF can regulate V(D)J recombination by segregating RSSs into distinct loop domains and inhibiting RSS synapsis, independent of any effects on transcription, RSS accessibility and RAG tracking. RAG-initiatd Tcrd D segment rearrangements in developing thymocytes were generated by deep sequencing using illumine Miseq

2016-09-02 | E-GEOD-81351 | biostudies-arrayexpress

Chromatin interactions involving super-enhancers associate with specific expression patterns of target genes

Project description:Super-enhancers may regulate target genes through chromatin looping. We connected super-enhancers in the K562 chronic myelogenous leukemia cell line with chromatin interactions identified from Chromatin Interaction Analysis with Paired-End Tag (ChIA-PET) data. Gene expression at proximal elements that are connected with distal super-enhancers showed significantly higher cell-type specificity than at proximal elements connected with other elements or not involved in interaction. 4C and Episwitch analysis of chromatin interactions showed that certain chromatin interactions are cell-specific, but others are more general. While super-enhancers upstream of c-MYC at the MYC-335 element can be found in other cancers, only super-enhancers downstream of c-MYC can be found in K562. 4C analysis of the c-MYC promoter revealed no chromatin interactions that are directed upstream of c-MYC, but only downstream of c-MYC, in the PVT1 long non-coding RNA gene. Cell-specific usage of super-enhancers could explain why the MYC-335 element that is associated with many solid cancers such as colorectal cancer and breast cancer, but not with leukemia. Surprisingly, we found that a chromatin interaction between c-MYC and a c-MYC super-enhancer is lost in chronic myelogenous leukemia patient blood as compared with blood from individuals without the disease through Oxford Biodynamicsâ?? Episwitch analysis. These results provide evidence for fine-tuning of expression patterns, such as cell-specific regulation of target genes by distal super-enhancers through chromatin interactions and an association between chromatin interactions and disease, and highlight that super-enhancers are more complex than previously described. Examination of several chromatin interactions involving super-enhancers using 4C-Seq and Episwitch (TM)

2017-05-01 | E-GEOD-77125 | biostudies-arrayexpress

Tandem CTCF sites function as insulators to balance spatial chromatin contacts and topological enhancer-promoter selection [V]

Project description:CTCF is a key insulator-binding protein and mammalian genomes contain numerous CTCF-binding sites (CBSs), many of which are organized in tandem arrays. Here we provide direct evidence that CBSs, if located between enhancers and promoters in the clustered Pcdh and b-globin clusters, function as an enhancer-blocking insulator by forming distinct directional chromatin loops, regardless whether enhancers contain CBS or not. Moreover, computational simulation and experimental capture revealed balanced promoter usage in vivo in cell populations and stochastic monoallelic expression in single cells by large arrays of tandem variable CBSs. Finally, gene expression levels are negatively correlated with CBS insulators located between enhancers and promoters on a genome-wide scale. Thus, single CBS insulators ensure proper enhancer insulation and promoter activation while tandem-arrayed CBS insulators determine balanced promoter choice. This finding has interesting implications on the role of topological insulators in 3D genome folding and developmental gene regulation.

2020-03-01 | GSE139679 | GEO

Tandem CTCF sites function as insulators to balance spatial chromatin contacts and topological enhancer-promoter selection [III]

2020-03-01 | GSE138645 | GEO

Tandem CTCF sites function as insulators to balance spatial chromatin contacts and topological enhancer-promoter selection [I]

2020-03-01 | GSE135394 | GEO

Tandem CTCF sites function as insulators to balance spatial chromatin contacts and topological enhancer-promoter selection [II]

2020-03-01 | GSE136328 | GEO