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Locus folding mechanisms determine modes of antigen receptor gene assembly (RNA-seq)

ABSTRACT: The dynamic folding of genomes regulates numerous biological processes, including antigen receptor (AgR) gene assembly. We show that, unlike other AgR loci, homotypic chromatin interactions and bi-directional chromosome looping both contribute to structuring Tcrb for efficient long-range V(D)J recombination. Inactivation of the CTCF binding element (CBE) or promoter at the most 5’Vβ segment (Trbv1) impaired loop extrusion originating locally and extending to DβJβ CBEs at the opposite end of Tcrb. Promoter or CBE mutation nearly eliminated Trbv1 contacts and decreased RAG endonuclease-mediated Trbv1 recombination. Importantly, Trbv1 rearrangement can proceed independent of substrate orientation, ruling out scanning by DβJβ-bound RAG as the sole mechanism of Vβ recombination, distinguishing it from Igh. Our data indicate that CBE-dependent generation of loops cooperates with promoter-mediated activation of chromatin to juxtapose Vβ and DβJβ segments for recombination through diffusion-based synapsis. Thus, the mechanisms that fold a genomic region can influence molecular processes occurring in that space, which may include recombination, repair, and transcriptional programming.

ORGANISM(S): Mus musculus

PROVIDER: GSE249648 | GEO | 2024/01/04

REPOSITORIES: GEO

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Locus folding mechanisms determine modes of antigen receptor gene assembly (ChIP-seq)

Project description:The dynamic folding of genomes regulates numerous biological processes, including antigen receptor (AgR) gene assembly. We show that, unlike other AgR loci, homotypic chromatin interactions and bi-directional chromosome looping both contribute to structuring Tcrb for efficient long-range V(D)J recombination. Inactivation of the CTCF binding element (CBE) or promoter at the most 5’Vβ segment (Trbv1) impaired loop extrusion originating locally and extending to DβJβ CBEs at the opposite end of Tcrb. Promoter or CBE mutation nearly eliminated Trbv1 contacts and decreased RAG endonuclease-mediated Trbv1 recombination. Importantly, Trbv1 rearrangement can proceed independent of substrate orientation, ruling out scanning by DβJβ-bound RAG as the sole mechanism of Vβ recombination, distinguishing it from Igh. Our data indicate that CBE-dependent generation of loops cooperates with promoter-mediated activation of chromatin to juxtapose Vβ and DβJβ segments for recombination through diffusion-based synapsis. Thus, the mechanisms that fold a genomic region can influence molecular processes occurring in that space, which may include recombination, repair, and transcriptional programming.

2024-01-04 | GSE249647 | GEO

Locus folding mechanisms determine modes of antigen receptor gene assembly (Hi-C)

2024-01-04 | GSE249646 | GEO

A Unifying Model for Molecular Determinants of the Pre-selection Vb Repertoire [RNA-Seq]

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2013-08-14 | E-GEOD-49233 | biostudies-arrayexpress

A Unifying Model for Molecular Determinants of the Pre-selection Vb Repertoire [RNA-Seq]

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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

A Unifying Model for Molecular Determinants of the Pre-selection Vβ Repertoire [ChIP-chip]

Project description:Chip-chip from pro-T(DN) cells from Rag1KO mice for H3K27ac, P300 and FAIRE The primary antigen receptor repertoire is sculpted by the process of V(D)J recombination, which must strike a balance between diversification and favoring gene segments with specialized functions. The precise determinants of how often gene segments are chosen to complete variable region coding exons remain elusive. We have quantified Vβ usage in the pre-selection Tcrb repertoire and report relative contributions of 14 distinct features in shaping their recombination efficiencies, including transcription, chromatin environment, spatial proximity to their DβJβ targets, and quality of recombinase recognition elements. Computational analyses provide a unifying model, revealing a minimal set of eight parameters that are predictive of Vβusage, dominated by chromatin modifications associated with transcription, but largely independent of the precise spatial proximity to DβJβclusters.

2013-08-14 | GSE42851 | GEO

On-target and Off-target Activities of RAG Are Restricted by Topological Chromatin Domains

Project description:RAG initiates V(D)J recombination in developing lymphocytes by generating "on-target" DNA double-stranded breaks at bona fide recombination signal sequence (RSS) pairs. We now employ RAG-generated DNA breaks in endogenous or ectopically-inserted RSS pairs as bait to identify huge numbers of RAG "off-target" sites. These off-target DNA breaks occur across convergent CTCF-binding element (CBE)-flanked loop domains containing the bait RSS pairs. Such off-target cleavage occurs at the simple CAC motif that defines the RSS cleavage-site and shows orientation-dependence best explained by a two-dimensional tracking mechanism. Deletion of the CBE-based IGCR1 IgH regulatory element disrupts antibody IgH recombination domains and, correspondingly, alters distributions of RAG on- and off-targets across the IgH locus. RAG off-targets frequently involved in chromosomal translocations occur in convergent RSS pairs at enhancer regions within a loop. Our findings reveal how RAG is developmentally focused and re-focused in lymphocytes and implicate mechanisms by which chromatin domains harness biological processes within them. We performed high-throughput genome-wide translocation sequencing (HTGTS) in progenitor B cells or cell lines to study signatures of RAG on and off-targeting activity using RAG-generated breaks in endogenous or ectopically-inserted paired bona fide RSSs as bait. Sequenceing was dong by Illumina Miseq.

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An ectopic CTCF binding element disturbs Vδ usage at the mouse Tcra-Tcrd locus by regulating contact between Vδ and Dδ 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 Eδ 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.

2016-09-02 | GSE81351 | GEO

On-target and Off-target Activities of RAG Are Restricted by Topological Chromatin Domains

2015-09-15 | GSE73007 | GEO

CTCF-Binding Elements Mediate Accessibility of RAG Substrates During Chromatin Scanning [dataset 1]

Project description:RAG endonuclease initiates antibody heavy chain variable region exon assembly from V, D, and J segments within a chromosomal V(D)J recombination center (RC) by cleaving between paired gene segments and flanking recombination signal sequences (RSSs). The IGCR1 control region promotes DJH intermediate formation by isolating Ds, JHs, and RC from upstream VHs in a chromatin loop anchored by CTCF-binding elements ("CBEs"). How VHs access the DJHRC for VH to DJH rearrangement was unknown. We report that CBEs immediately downstream of frequently rearranged VH-RSSs increase recombination potential of their associated VH far beyond that provided by RSSs alone. This CBE activity becomes particularly striking upon IGCR1 inactivation, which allows RAG, likely via loop extrusion, to linearly scan chromatin far upstream. VH-associated CBEs stabilize interactions of D-proximal VHs first encountered by the DJHRC during linear RAG scanning and, thereby, promote dominant rearrangement of these VHs by an unanticipated chromatin accessibility-enhancing CBE function.

2018-07-03 | GSE112781 | GEO

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