Project description:Our studies have revealed that a large class of CTCF binding sites – namely the upstream sites – conform neither to a conformational nor a local recombinase activating role. Their conserved spatial distances upstream of V gene segments suggests a possible role in insulating V gene segments from neighboring V gene segments. In any case, understanding the sequence determinants of CTCF binding to the murine IgH locus should facilitate future studies evaluating how IgH locus accessibility regulates CTCF binding as well as the functions that CTCF plays in regulating the recombinational accessibility of VH gene segments during B cell development.
Project description:Numerous B-cell lymphomas feature translocations linking oncogenes with the IgH locus and epigenetic drugs such as histone deacetylase inhibitors (HDACi) have been approved to treat some of them. In this study we investigated IgH locus transcription in B-cell splenocytes stimulated with LPS and the HDACi SAHA. B-cell development is spatially and temporally regulated with the 3'RR enhancer of the IgH locus as a conductor. 3'RR is composed of 4 enhancer elements with a palindromic structure of great significance. We investigated the role of this palindrome with KOKI mice where the 30Kb structure of the 3'RR has been deleted of its palindromic structure.
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.
Project description:Antigen receptor assembly in lymphocytes involves stringently-regulated coordination of specific DNA rearrangement events across several large chromosomal domains. Previous studies indicate that transcription factors such as paired box 5 (PAX5), Yin Yang 1 (YY1), and CCCTC-binding factor (CTCF) play a role in regulating the accessibility of the antigen receptor loci to the V(D)J recombinase, which is required for these rearrangements. To gain clues about the role of CTCF binding at the murine immunoglobulin heavy chain (IgH) locus, we utilized a computational approach that identified 144 putative CTCF-binding sites within this locus. We found that these CTCF sites share a consensus motif distinct from other CTCF sites in the mouse genome. Additionally, we could divide these CTCF sites into three categories: intergenic sites remote from any coding element, upstream sites present within 8 kb of the VH-leader exon, and recombination signal sequence (RSS)-associated sites characteristically located at a fixed distance (?18 bp) downstream of the RSS. We noted that the intergenic and upstream sites are located in the distal portion of the VH locus, whereas the RSS-associated sites are located in the DH-proximal region. Computational analysis indicated that the prevalence of CTCF-binding sites at the IgH locus is evolutionarily conserved. In all species analyzed, these sites exhibit a striking strand-orientation bias, with >98% of the murine sites being present in one orientation with respect to VH gene transcription. Electrophoretic mobility shift and enhancer-blocking assays and ChIP-chip analysis confirmed CTCF binding to these sites both in vitro and in vivo.
Project description:We propose that multiple CTCF sites on same motif orientation could cooperate with each other for stable enhancer-promoter interactions in the β-globin locus.
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 pax5-/- rag2-/- pro-B cells. Chip-Chip with one experiment for each antibody, 12 samples.
Project description:The immunoglobulin heavy-chain (Igh) locus undergoes large-scale contraction in pro-B cells, which facilitates VH-DJH recombination by juxtaposing distal VH genes next to the DJH- rearranged gene segment in the proximal Igh domain. By high-resolution mapping of long-range interactions, we now demonstrate that an array of local interaction domains establishes the three- dimensional structure of the extended Igh locus in lymphoid progenitors and thymocytes. In pro- B cells, these local domains engage in long-range interactions across the entire Igh locus, which depend on the transcription factors Pax5, YY1 and CTCF. The large VH gene cluster thereby undergoes flexible long-range interactions with the more rigidly structured 3M-bM-^@M-^Y proximal domain, which ensures that all VH genes can participate with similar probability in VH-DJH recombination to generate a diverse antibody repertoire. Notably, these long-range interactions appear to be an intrinsic feature of the VH gene cluster, as they are still generated upon mutation of the EM-NM-< enhancer, IGCR1 insulator or 3M-bM-^@M-^Y regulatory region present in the 3M-bM-^@M-^Y proximal Igh domain. 4C sequencing from mutliple celltypes with multiple viewpoints; uneven number of replicates ChIP-Seq
Project description:CTCF binding sites are frequently mutated in cancer, but how these mutations accumulate and whether they broadly perturb CTCF binding is not well understood. We report that skin cancers exhibit a highly-specific asymmetric mutation pattern within CTCF motifs attributable to ultraviolet irradiation and differential nucleotide excision repair (NER). CTCF binding site mutations form independent of replication timing and are enriched at sites of CTCF/cohesin complex binding, suggesting a role for cohesin in stabilizing CTCF-DNA binding and impairing NER. Performing CTCF ChIP-seq in a melanoma cell-line, we show CTCF binding site mutations to be functional by demonstrating allele-specific reduction of CTCF binding to mutant alleles. While topologically-associating domains with mutated CTCF anchors in melanoma contain differentially-expressed cancer-associated genes, CTCF motif mutations appear generally under neutral selection. However, the frequency and potential functional impact of such mutations in melanoma highlights the need to consider their impact on cellular phenotype in individual genomes.
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.