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The establishment of a CTCF activity reporter for systematic stratification of CTCF binding sites

ABSTRACT: While the elements encoding enhancers and promoters have been relatively well studied, the full spectrum of insulator elements which bind the CCCTC binding factor (CTCF), is relatively poorly characterised. In part, this is due the fact that their roles and activity is greatly influenced by their genomic context. Here we have developed an experimental system to determine the ability of consistently sized, individual CTCF elements to interpose between enhancers and promoters and thereby reduce gene expression during differentiation. Importantly each element is tested in the identical location thereby minimising the effect of genomic context. We found no correlation between the ability of CTCF elements to block enhancer-promoter activity with the amount of CTCF or cohesin bound at the natural genomic sites of these elements; the degree of evolutionary conservation; or their resemblance to the consensus core sequences. Nevertheless, we have shown that the strongest enhancer-promoter blockers include a previously described bound element lying upstream of the CTCF core motif. In addition, we found other uncharacterised DNAse1 footprints located close to the core sequence that may affect function. We have developed a high throughput assay of CTCF elements which will enable researchers to sub-classify CTCF elements in an unbiased way.

ORGANISM(S): Mus musculus

PROVIDER: GSE240678 | GEO | 2023/08/12

REPOSITORIES: GEO

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Comparative analyses of CTCF and BORIS occupancies uncover two distinct classes of CTCF binding genomic regions

Project description:CTCF and BORIS (CTCFL), two paralogous mammalian proteins sharing nearly identical DNA binding domains, are thought to function in mutually exclusive manners in DNA binding and transcriptional regulation. Here we show that these two proteins co-occupy a specific subset of regulatory elements consisting of clustered CTCF binding motifs (termed 2xCTSes). BORIS occupancy at 2xCTSes is largely invariant in BORIS-positive cancer cells, with the genomic pattern recapitulating the germline-specific BORIS binding to chromatin. In contrast to the single-motif CTCF target sites (1xCTSes), the 2xCTS elements are preferentially found at active promoters and enhancers, both in cancer and germ cells. 2xCTSes are also enriched in genomic regions that escape histone to protamine replacement in human and mouse sperm. Depletion of BORIS gene leads to altered transcription of a large number of genes and the differentiation of K562 cells, while the ectopic expression of this CTCF paralog leads to specific changes in transcription in MCF7 cells. In summary, we discover two functionally and structurally different classes of CTCF binding regions, 2xCTSes and 1xCTSes, revealed by their predisposition to bind BORIS. We propose that 2xCTSes play key roles in the transcriptional program of cancer and germ cells Genome-wide mapping of CTCF and BORIS occupancies in both germ and cancer cells. ChIP-seq and expression profiling by high throughput sequencing

2015-07-23 | E-GEOD-70764 | biostudies-arrayexpress

CTCF binding polarity determines chromatin looping [4C]

Project description:CCCTC-binding factor (CTCF) is an architectural protein involved in the three-dimensional organization of chromatin. In this study, we systematically assayed the 3D genomic contact profiles of hundreds of CTCF binding sites in multiple tissues with high-resolution 4C-seq. We find both developmentally stable and dynamic chromatin loops. As recently reported, our data also suggest that chromatin loops preferentially form between CTCF binding sites oriented in a convergent manner. To directly test this, we used CRISPR-Cas9 genome editing to delete core CTCF binding sites in three loci, including the CTCF site in the Sox2 super-enhancer. In all instances, CTCF and cohesin recruitment were lost, and chromatin loops with distal CTCF sites were disrupted or destabilized. Re-insertion of oppositely oriented CTCF recognition sequences restored CTCF and cohesin recruitment, but did not re-establish chromatin loops. We conclude that CTCF binding polarity plays a functional role in the formation of higher order chromatin structure. 4C-seq was performed on a large number of viewpoints in E14 embryonic stem cells, neural precursor cells and primary fetal liver cells

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Project description:Ctcf and cohesin are key players in the three dimensional organization of chromatin. Whereas genome-wide Ctcf binding has diverged substantially between species due to transposon-mediated motif expansions, demarcation of topologically associating domains (TADs) by Ctcf is remarkably well conserved. Yet, the Ctcf consensus motif poorly predicts TADs and the majority of Ctcf sites are not at TAD boundaries. Here we demonstrate that the ChAHP complex (Chd4, Adnp, HP1) competes with Ctcf for a common set of genomic binding sites. In absence of ChAHP, novel insulated regions are formed at ChAHP bound sites, whereas proximal canonical boundaries are weakened. These data reveal that Ctcf-mediated loop formation is modulated by a distinct zinc-finger protein complex. Strikingly, ChAHP bound loci are mainly situated within evolutionary young SINE B2 transposable elements. This further implicates ChAHP in maintenance of evolutionary conserved spatial chromatin organization by buffering novel Ctcf binding sites that emerged through SINE expansions.

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2016-08-17 | GSE84326 | GEO

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2019-11-12 | PXD014441 | Pride

CTCF-dependent enhancer hijacking by the EVI1 oncogene in leukemia

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IGH analysis in pro-B cells with H3K4me3, H3K4me2, H3K9ac, H3K27me3, Pax5 and CTCF [ChIP-Seq]

Project description:VH-DJH recombination of the immunoglobulin heavy-chain (Igh) locus is temporally and spatially controlled during early B-cell development, and yet no regulatory elements other than the VH gene promoters have been identified throughout the entire 2.5-Mb VH gene cluster. Here we discovered novel regulatory sequences that are interspersed in the distal VH gene region. These conserved repeat elements were characterized by the presence of Pax5-dependent active chromatin, the binding of Pax5, E2A, CTCF and Rad21 as well as by Pax5-dependent antisense transcription in pro-B cells. The Pax5-activated intergenic repeat (PAIR) elements were no longer bound by Pax5 in pre-B and B cells consistent with the loss of antisense transcription, whereas E2A and CTCF interacted with PAIR elements throughout early B-cell development. The pro-B-cell-specific and Pax5-dependent activity of the PAIR elements suggests that they are involved in the regulation of distal VH-DJH recombination at the Igh locus. Analysis of chromatin and TF binding in rag2-/- and wt pro-B, DP T and Mature B cells. Chip-Seq of CTCF and Rad21. The provided data is in mm8 coordinates.

2011-02-11 | E-GEOD-27214 | biostudies-arrayexpress

CTCF binding profiles in Drosophila melanogaster 3rd instar larva T1 and T3 leg discs

Project description:Although the majority of genomic binding sites for the insulator protein CTCF are constitutively occupied, a subset show variable occupancy. Such variable sites provide an opportunity to assess context-specific CTCF functions in gene regulation. Here we have identified a variably occupied CTCF site in the Ultrabithorax (Ubx) gene in Drosophila. This site is occupied in tissues where Ubx is active (third thoracic imaginal leg disc) but is not bound in tissues where the Ubx gene is repressed (first thoracic imaginal leg disc). Comparison of CTCF binding in T1 leg disc vs T3 leg disc in from 3rd instar larva

2014-10-11 | E-GEOD-62234 | biostudies-arrayexpress

CTCF demarcates chromatin domains

Project description:Insulators are DNA elements, which prevent inappropriate interactions between the neighboring regions of the genome. They can be functionally classified as either enhancer blockers or domain barriers. CTCF (CCCTC binding factor) is the only known major insulator binding protein in the vertebrates and has been shown to bind many enhancer-blocking elements. However, it is not clear whether it plays a role in chromatin domain barriers between active and repressive domains. Here, we used ChIP-Seq to map the genome-wide binding sites of CTCF in three cell types and identified significant binding of CTCF to the boundaries of repressive chromatin domains marked by H3K27me3. Although we find an extensive overlapping of CTCF binding sites across the three cell types, its association with the domain boundaries is cell type-specific. We further show that the nucleosomes flanking CTCF binding sites are well positioned and associated with histone H2AK5 acetylation (H2AK5ac). Interestingly, we found a complementary pattern between the repressive H3K27me3 and the active H2AK5ac regions, which are separated by CTCF. Our findings indicate that CTCF may play important roles in the barrier activity of insulators and provide a resource for further investigation of the CTCF function in organizing chromatin in the human genome. Examination of the role of CTCF in chromatin domain barrier function In addition to the ChIP-seq analysis, two replicates of HeLa expression data were studied.

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A genome-wide map of CTCF multivalency redefines the CTCF code

Project description:The “CTCF code” hypothesis posits that CTCF pleotropic functions are driven by recognition of diverse DNA sequences through combinatorial use of its 11 zinc fingers (ZFs). This model however is supported by in vitro binding studies of a limited number of sequences. To directly test CTCF multivalency in vivo we here define ZF binding requirements at ~50,000 genomic sites in primary lymphocytes. We find that CTCF reads sequence diversity through ZF clustering. ZFs4-7 anchor CTCF to ~80% of targets containing the 20bp core motif. Non-conserved flanking sequences are recognized by ZFs1-2 and ZFs8- 11 clusters, which also stabilize CTCF broadly. Alternatively, CTCF employ ZFs9-11 to associate with a second phylogenetically-conserved upstream motif at ~15% of its sites. Individually, ZFs increase overall binding affinity and chromatin residence time. Unexpectedly, we also uncover a conserved downstream DNA motif that destabilizes CTCF occupancy. CTCF thus associates with a wide array of DNA modules via combinatorial clustering of its 11 ZFs.

2011-11-19 | GSE33819 | GEO

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