Active and inactive enhancers co-operate to exert localized and long-range control of gene regulation [RNA-seq]
Ontology highlight
ABSTRACT: We report that in developing B cells individual enhancers of Igk make up super-enhancer cluster where contacts between its components rely on all constituents. Reduction of interaction frequency in enhancer knock-out cells is associated with deminished transcriptional output of enhancers and Igk locus. Moreover, we find that Igk enhancer MiEk has an effect on levels of CBFb enrichment on Tcrb enhancer, Eb afffecting Tcrb recombination and T cell development.
Project description:We report that in developing B cells individual enhancers of Igk make up super-enhancer cluster where contacts between its components rely on all constituents. Reduction of interaction frequency in enhancer knock-out cells is associated with deminished transcriptional output of enhancers and Igk locus. Moreover, we find that Igk enhancer MiEk has an effect on levels of CBFb enrichment on Tcrb enhancer, Eb afffecting Tcrb recombination and T cell development.
Project description:We report that in developing B cells individual enhancers of Igk make up super-enhancer cluster where contacts between its components rely on all constituents. Reduction of interaction frequency in enhancer knock-out cells is associated with deminished transcriptional output of enhancers and Igk locus. Moreover, we find that Igk enhancer MiEk has an effect on levels of CBFb enrichment on Tcrb enhancer, Eb afffecting Tcrb recombination and T cell development.
Project description:We report that in developing B cells individual enhancers of Igk make up super-enhancer cluster where contacts between its components rely on all constituents. Reduction of interaction frequency in enhancer knock-out cells is associated with deminished transcriptional output of enhancers and Igk locus. Moreover, we find that Igk enhancer MiEk has an effect on levels of CBFb enrichment on Tcrb enhancer, Eb afffecting Tcrb recombination and T cell development.
Project description:During B cell development the precursor B cell receptor (pre-BCR) checkpoint is thought to increase immunoglobulin k light chain (Igk) locus accessibility to the V(D)J recombinase. Accordingly, pre-B cells lacking the pre-BCR signaling molecules Btk or Slp65 showed reduced germline Vk transcription. To investigate whether pre-BCR signaling modulates Vk accessibility through enhancer-mediated Igk locus topology, we performed chromosome conformation capture and sequencing analyses. These revealed that already in pro-B cells the k enhancers robustly interact with the ~3.2 Mb Vk region and its flanking sequences. Analyses in wild-type, Btk and Slp65 single and double-deficient pre-B cells demonstrated that pre-BCR signaling reduces interactions of both enhancers with Igk locus flanking sequences and increases interactions of the 3â??k enhancer with Vk genes. Remarkably, pre-BCR signaling does not significantly affect interactions between the intronic enhancer and Vk genes, which are already robust in pro-B cells. Both enhancers interact most frequently with highly used Vk genes, which are often marked by transcription factor E2a. We conclude that the k enhancers interact with the Vk region already in pro-B cells and that pre-BCR signaling induces accessibility through a functional redistribution of long-range chromatin interactions within the Vk region, whereby the two enhancers play distinct roles. We performed genome-wide expression profiling of FACS-purified B220+CD19+ pre-B cell fractions from wild-type (WT), Btk and Slp65 single and double deficient VH81x transgenic Rag1-/- mice (n=4 of each genotype). In these experiments non-VH81x transgenic Rag1-/- pro-B cells served as controls (n=3).
Project description:V(D)J recombination relies on the presence of proximal enhancers that activate the antigen receptor (AgR) loci in a lineage- and stage-specific manner. Unexpectedly, we find that both active and inactive AgR enhancers cooperate to disseminate their effects in a localized and long-range manner. Here, we demonstrate the importance of short-range contacts between active enhancers that constitute an Igk super-enhancer in B cells. Deletion of one element reduces the interaction frequency between other enhancers in the hub, which compromises the transcriptional output of each component. Furthermore, we establish that, in T cells, long-range contact and cooperation between the inactive Igk enhancer MiEκ and the active Tcrb enhancer Eβ alters enrichment of CBFβ binding in a manner that impacts Tcrb recombination. These findings underline the complexities of enhancer regulation and point to a role for localized and long-range enhancer-sharing between active and inactive elements in lineage- and stage-specific control.
Project description:During B cell development the precursor B cell receptor (pre-BCR) checkpoint is thought to increase immunoglobulin k light chain (Igk) locus accessibility to the V(D)J recombinase. Accordingly, pre-B cells lacking the pre-BCR signaling molecules Btk or Slp65 showed reduced germline Vk transcription. To investigate whether pre-BCR signaling modulates Vk accessibility through enhancer-mediated Igk locus topology, we performed chromosome conformation capture and sequencing analyses. These revealed that already in pro-B cells the k enhancers robustly interact with the ~3.2 Mb Vk region and its flanking sequences. Analyses in wild-type, Btk and Slp65 single and double-deficient pre-B cells demonstrated that pre-BCR signaling reduces interactions of both enhancers with Igk locus flanking sequences and increases interactions of the 3’k enhancer with Vk genes. Remarkably, pre-BCR signaling does not significantly affect interactions between the intronic enhancer and Vk genes, which are already robust in pro-B cells. Both enhancers interact most frequently with highly used Vk genes, which are often marked by transcription factor E2a. We conclude that the k enhancers interact with the Vk region already in pro-B cells and that pre-BCR signaling induces accessibility through a functional redistribution of long-range chromatin interactions within the Vk region, whereby the two enhancers play distinct roles.
Project description:Regulatory T (Treg) cells, whose identity and function are defined by the transcription factor Foxp3, are indispensable for immune homeostasis. It is unclear whether Foxp3 exerts its Treg lineage specification function through active modification of the chromatin landscape and establishment of new enhancers or by exploiting a pre-existing enhancer landscape. Analysis of the chromatin accessibility of Foxp3-bound enhancers in Treg and Foxp3-negative T cells showed that Foxp3 was bound overwhelmingly to pre-accessible enhancers occupied by its cofactors in precursor cells or a structurally related predecessor. Furthermore, the bulk of Foxp3-bound Treg cell enhancers lacking in Foxp3- CD4+ cells became accessible upon T cell receptor activation prior to Foxp3 expression with only a small subset associated with several functionally important genes being exclusively Treg cell-specific. Thus, in a late cellular differentiation process Foxp3 defines Treg cell functionality in an “opportunistic” manner by largely exploiting the preformed enhancer network instead of establishing a new enhancer landscape. Four transcription factors (Foxp3, Ets1, Elf1, and Cbfb) were immunoprecipated while crosslinked to chromatin. These experiments were then combined with DNase-seq data (being uploaded separately as part of ENCODE project) to find that Foxp3 binds exclusively to open chromatin. Data was also leveraged from GSE40657 and GSE33653.
Project description:Tcrb locus V(D)J recombination is regulated by positioning at the nuclear periphery. Here we used DamID to profile Tcrb locus interactions with the nuclear lamina at high-resolution. We identified a lamina-associated domain (LAD) border composed of several CTCF binding elements that segregates active non-LAD from inactive LAD regions of the locus. Deletion of the LAD border caused an enhancer-dependent spread of H3K27ac from the active recombination center into recombination center-proximal LAD chromatin. This was associated with a disruption to LAD organization, increased chromatin looping to the recombination center, and increased transcription and recombination of recombination center-proximal gene segments. Our results show that a Tcrb locus LAD and LAD border are critical components of Tcrb locus gene regulation and suggest that LAD borders may generally function to constrain the activity of nearby enhancers.