Jk DNA GAGA MOTIFS ARE REQUIRED FOR LOCAL NUCLEOSOME REMODELING AND Vk-Jk RECOMBINATION [ATAC-Seq]
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE288585 | GEO | 2026/01/14
REPOSITORIES: GEO
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Project description:Immunoreceptor gene recombination requires complementary 12 bp and 23 bp recombination signal sequences (RSSs). In addition, the RSSs that assemble the RAG proteins, recombination centers, must be accessible yet flanked by a 5’ nucleosome decorated with H3K4me3. In Drosophila, DNA GAGA motifs play an important role in nucleosome positioning. Herein, we report that 5’ to each functional Jk RSS is a DNA GAGA motif conserved across mammalian species. In mice, the GAGA motif 5’ to Jk1 regulated local RSS accessibility and 5’ nucleosome placement. Furthermore, it was required for Vk-Jk1 recombination. Murine Jk3 is nonfunctional, having mutations in both RSS and GAGA motifs. Restoring both GAGA and RSS motifs rescued Vk-Jk3 recombination. In contrast, restoring the RSS alone did not. Genome-wide, strong cryptic 23 RSSs were preferentially bound to nucleosomes. Furthermore, evolutionary selection against cRSS only occurred in the A Compartment of B lymphocytes, not embryonic stem cells. These data indicate that in developing B cells, nucleosome positioning both enables and restricts recombination to Jk. Furthermore, our data suggest an expanded definition of recombination center-associated RSSs to include a 5’ GAGA sequence that dictates the local epigenetic state required for gene recombination.
2026-01-14 | GSE288584 | GEO
Project description:In developing B lymphocytes, V(D)J recombination assembles IgH and Igk variable region exons from hundreds of gene segments clustered across mega-base Igh and Igk loci. V, D, and J segments are flanked by conserved recombination signal sequences (RSSs) that target RAG endonuclease. RAG orchestrates Igh V(D)J recombination upon capturing a JH-RSS within the JH-RSS-based recombination center (RC). JH-RSS orientation programs RAG to scan upstream D- and VH-containing chromatin linearly presented by cohesin-mediated loop extrusion. During Igh scanning, RAG robustly utilizes only D- or VH-RSSs in convergent ("deletional") orientation with JH-RSSs. However, for Vk-to-Jk joining, RAG utilizes Vk-RSSs from deletional- and inversional-oriented clusters, inconsistent with linear scanning. Here, we elucidate the Vk-to-Jk joining mechanism. Igk undergoes robust primary and secondary rearrangements, which confounds scanning assays. Thus, we engineered cells to undergo only primary Vk-to-Jk rearrangements and found that RAG-scanning from the primary Jk-RC terminates just 8kb upstream within the CTCF-Site-based Sis element. While Sis and the Jk-RC barely interacted with the Vk locus, the CTCF-site-based Cer element, 4kb upstream of Sis, interacted with various loop-extrusion impediments across the locus. Like VH-locus inversion, DJH inversion abrogated VH-to-DJH joining; yet Vk-locus or Jk inversion allowed robust Vk-to-Jk joining. Together, these experiments implicated loop extrusion in bringing Vks near Cer for short-range diffusion-mediated capture by RC-based RAG. To elucidate key mechanistic elements for diffusional V(D)J recombination in Igk versus Igh, we assayed Vk-to-JH and D-to-Jk rearrangements in hybrid Igh-Igk loci generated by targeted chromosomal translocations, and pinpointed remarkably strong Vk and Jk RSSs. Indeed, RSS replacements in hybrid or normal Igk and Igh loci confirmed ability of Igk versus Igh RSSs to promote robust diffusional joining. We propose that Igk evolved strong RSSs to mediate diffusional Vk-to-Jk joining; while Igh evolved weaker RSSs requisite for modulating VH joining by RAG scanning impediments.
2024-04-08 | GSE254039 | GEO
Project description:In developing B lymphocytes, V(D)J recombination assembles IgH and Igk variable region exons from hundreds of gene segments clustered across mega-base Igh and Igk loci. V, D, and J segments are flanked by conserved recombination signal sequences (RSSs) that target RAG endonuclease. RAG orchestrates Igh V(D)J recombination upon capturing a JH-RSS within the JH-RSS-based recombination center (RC). JH-RSS orientation programs RAG to scan upstream D- and VH-containing chromatin linearly presented by cohesin-mediated loop extrusion. During Igh scanning, RAG robustly utilizes only D- or VH-RSSs in convergent ("deletional") orientation with JH-RSSs. However, for Vk-to-Jk joining, RAG utilizes Vk-RSSs from deletional- and inversional-oriented clusters, inconsistent with linear scanning. Here, we elucidate the Vk-to-Jk joining mechanism. Igk undergoes robust primary and secondary rearrangements, which confounds scanning assays. Thus, we engineered cells to undergo only primary Vk-to-Jk rearrangements and found that RAG-scanning from the primary Jk-RC terminates just 8kb upstream within the CTCF-Site-based Sis element. While Sis and the Jk-RC barely interacted with the Vk locus, the CTCF-site-based Cer element, 4kb upstream of Sis, interacted with various loop-extrusion impediments across the locus. Like VH-locus inversion, DJH inversion abrogated VH-to-DJH joining; yet Vk-locus or Jk inversion allowed robust Vk-to-Jk joining. Together, these experiments implicated loop extrusion in bringing Vks near Cer for short-range diffusion-mediated capture by RC-based RAG. To elucidate key mechanistic elements for diffusional V(D)J recombination in Igk versus Igh, we assayed Vk-to-JH and D-to-Jk rearrangements in hybrid Igh-Igk loci generated by targeted chromosomal translocations, and pinpointed remarkably strong Vk and Jk RSSs. Indeed, RSS replacements in hybrid or normal Igk and Igh loci confirmed ability of Igk versus Igh RSSs to promote robust diffusional joining. We propose that Igk evolved strong RSSs to mediate diffusional Vk-to-Jk joining; while Igh evolved weaker RSSs requisite for modulating VH joining by RAG scanning impediments.
2024-04-08 | GSE263123 | GEO
Project description:V(D)J recombination, essential for adaptive immunity, is initiated by RAG1/2, which recognizes Recombination Signal Sequences (RSSs) flanking gene segments at Antigen Receptor (AgR) loci. RSSs comprise conserved heptamer and nonamer motifs separated by a 12/23-base spacer. While the first three heptamer nucleotides (5’-CAC) are strictly conserved, RSS promiscuity enables RAG “off-target” activity at RSS-like sequences, termed “cryptic RSSs” (cRSSs), contributing to chromosomal deletions and lymphoid tumorigenesis. Notably, the nonamer exhibits substantial sequence variability across physiological RSSs. In addition, many cRSSs lack a discernible nonamer-like sequence, limiting the ability to predict RAG targets based on RSS consensus. Using a high-throughput approach, we characterized here the nonamer properties supporting RAG-mediated recombination. While the consensus nonamer (5’-ACAAAAACC) exhibited strong functionality, numerous sequences significantly diverged from it promoted high recombination rate. These functional nonamers balance two, somewhat opposing, features: affinity for the RAG nonamer-binding domain (NBD) – primarily via a shared purine–weak–purine (RWR) motif at positions 4–6, and nucleosome repulsion. Moreover, nonamers of genomic cRSSs mimic canonical nonamers mainly through nucleosome-repelling sequences. This study provides a model for both physiological RAG activity and its off-target effects, enhancing our understanding of immune repertoire formation and the genetic basis of lymphoid cancers.
2025-12-30 | GSE300515 | GEO
Project description:Background: V(D)J recombination is an essential process for the generation of diverse antigen receptor (AgR) repertoires. In B cells, immunoglobulin kappa (Igk) light chain locus recombination follows recombination of the immunoglobulin heavy chain (Igh) locus. We recently developed the DNA-based VDJ-seq assay for the unbiased quantitation of Igh VH and DH repertoires. In conjunction with genome-wide datasets for several epigenetic features, we showed that two active chromatin states, located at the recombination signal sequences (RSS) of VH genes, are highly predictive of recombination. The contribution of chromatin features to Vk gene choice in recombination remains poorly understood. Results: We adapted the VDJ-seq assay to profile the Igk VkJk repertoire, and obtained a comprehensive readout of highly variable Vk gene usage in mouse bone marrow pre-B cells. We identified PU.1 binding at the RSS as highly predictive of whether a gene will actively recombine or not. Prediction of the frequency of recombination was more dependent on H3K4 methylation and IKAROS binding. Conclusions: Epigenetic features within the Vk region are able to explain much of the variation in Vk gene usage. Whilst PU.1 binding at the RSS appears to play a binary, all-or-nothing role, priming Vk genes for recombination, the frequency with which these genes recombine is shaped by the presence and enrichment of a number of other epigenetic features. In contrast to the Igh locus, the epigenetic landscape of the promoter as well as the RSS is predictive of Vk gene recombination.
2017-11-03 | GSE101606 | GEO
Project description:Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igk) locus, which recombines Jk and Vk gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igk folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igk V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vk usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vk joining. In CTCF N-terminal-deficient B cells, defects in inversional Vk joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vk-Jk intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igk repertoire.
2025-11-18 | PXD070894 | Pride
Project description:Interaction of the Kaposi’s sarcoma-associated herpesvirus (KSHV) Rta protein with the cellular Notch signaling effector, Recombination Signaling Protein (RBP)-Jk (aka CSL and CBF-1), is essential for viral reactivation from latency. We previously showed that Rta binds to a DNA motif repeated in the viral Mta promoter (called “CANT” or Rta-c) to stimulate RBP-Jk DNA binding, and distinguished Rta from the activated Notch-1 protein. To determine whether Rta’s mechanism would apply generally to other viral promoters, we employed chromatin immunoprecipitation/deep sequencing (ChIP/Seq) to identify Rta and RBP-Jk binding sites across the KSHV genome. We show that RBP-Jk binds nearly exclusively to unique genome sites during latency and reactivation. Many, but not all, reactivation-specific RBP-Jk peaks were associated with Rta bound to single Rta-c motifs. Other motifs that were over-represented with stimulated RBP-Jk DNA binding including those for the cellular DNA binding proteins BCL11A, MNT, MAF B, and TCF12. Four of the top seven motifs that were most over-represented with inhibition of RBP-Jk DNA binding were putative binding sites for the Pit/Oct/Unc (POU) family of proteins, including POU3F3 (Oct-8) and POU5F1 (Oct-4). Interestingly, two other POU motifs, including one for the POU2F1 (Oct-1) protein, are associated with inhibition of RBP-Jk DNA binding unless Rta bound to a nearby Rta-c motif. The relative distances between the Rta-c, POU, and RBP-Jk motifs were conserved at reactivation-specific RBP-Jk peaks in three promoters that Rta transactivated, and the Rta-c and Oct-1 motifs overlapped in two of those. The proximity of the Rta-c/Oct-1 motif to an RBP-Jk motif is critical for Rta transactivation of the ORF50AS/KbZIP promoter, and knockdown of Oct-1 protein debilitated reactivation and production of infectious virus. Our data suggest a broad role for POU proteins in regulating DNA binding of RBP-Jk and its associated transactivators.
2019-07-14 | GSE122752 | GEO
Project description:Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igk) locus, which recombines Jk and Vk gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igk folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igk V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vk usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vk joining. In CTCF N-terminal-deficient B cells, defects in inversional Vk joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vk-Jk intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igk repertoire.
2025-11-20 | GSE305325 | GEO
Project description:Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igk) locus, which recombines Jk and Vk gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igk folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igk V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vk usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vk joining. In CTCF N-terminal-deficient B cells, defects in inversional Vk joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vk-Jk intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igk repertoire.
2025-11-20 | GSE287937 | GEO
Project description:Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igk) locus, which recombines Jk and Vk gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igk folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igk V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vk usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vk joining. In CTCF N-terminal-deficient B cells, defects in inversional Vk joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vk-Jk intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igk repertoire.
2025-11-20 | GSE287935 | GEO