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BACH2 mediates negative selection and p53-dependent tumor suppression at the pre-B cell receptor checkpoint.

ABSTRACT: The B cell-specific BACH2 transcription factor is required for affinity maturation of mature B cells. Here, we show that Bach2 mediates negative selection at the pre-B cell receptor checkpoint and functions as a critical safeguard against leukemogenesis. Bach2-mediated activation of p53 is required for stringent elimination of pre-B cells that failed to productively rearrange immunoglobulin VH-DJH gene segments, and thus lack pre-B cell receptor expression. Upon productive VH-DJH gene rearrangement, pre-B cell receptor signaling ends negative selection through BCL6-mediated repression of p53. In patients with pre-B acute lymphoblastic leukemia, Bach2-mediated checkpoint control is frequently compromised and low levels of Bach2 expression represent a strong independent predictor of poor clinical outcome. Bach2+/+ pre-B cells resist leukemic transformation by Myc through Bach2-dependent upregulation of p53. Upon transformation with Myc, Bach2-/- pre-B cells fail to upregulate p53, form large colonies and initiate fatal leukemia in transplant recipient mice. ChIP-seq and gene expression analyses revealed that BACH2 competes with BCL6 for promoter binding and reverses BCL6-mediated repression of p53 and multiple other checkpoint control genes. These findings identify Bach2 as a key activator of p53 in pre-B cells, which is critical to maintain stringency of the pre-B cell receptor checkpoint and an important barrier against leukemic transformation. ChIP-seq using BACH2 and BCL6 antibodies in OCI-Ly7 cells

ORGANISM(S): Homo sapiens

SUBMITTER: Huimin Geng

PROVIDER: E-GEOD-44420 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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BACH2 mediates negative selection and p53-dependent tumor suppression at the pre-B cell receptor checkpoint.

Project description:The B cell-specific BACH2 transcription factor is required for affinity maturation of mature B cells. Here, we show that Bach2 mediates negative selection at the pre-B cell receptor checkpoint and functions as a critical safeguard against leukemogenesis. Bach2-mediated activation of p53 is required for stringent elimination of pre-B cells that failed to productively rearrange immunoglobulin VH-DJH gene segments, and thus lack pre-B cell receptor expression. Upon productive VH-DJH gene rearrangement, pre-B cell receptor signaling ends negative selection through BCL6-mediated repression of p53. In patients with pre-B acute lymphoblastic leukemia, Bach2-mediated checkpoint control is frequently compromised and low levels of Bach2 expression represent a strong independent predictor of poor clinical outcome. Bach2+/+ pre-B cells resist leukemic transformation by Myc through Bach2-dependent upregulation of p53. Upon transformation with Myc, Bach2-/- pre-B cells fail to upregulate p53, form large colonies and initiate fatal leukemia in transplant recipient mice. ChIP-seq and gene expression analyses revealed that BACH2 competes with BCL6 for promoter binding and reverses BCL6-mediated repression of p53 and multiple other checkpoint control genes. These findings identify Bach2 as a key activator of p53 in pre-B cells, which is critical to maintain stringency of the pre-B cell receptor checkpoint and an important barrier against leukemic transformation.

2013-06-27 | GSE44420 | GEO

Cooperative transcriptional repression by BCL6 and BACH2 in germinal center B-cell differentiation

Project description:The transcriptional repressors BCL6 and BACH2 are crucial regulators of germinal center (GC) B-cell fate, and are known to interact and repress transcription of PRDM1, a key driver of plasma cell differentiation. How these factors cooperate is not fully understood. Herein we show that while GC formation is only minimally impaired in Bcl6+/- or Bach2+/- mice, double heterozygous Bcl6+/-Bach2+/- mice exhibit profound reduction in GC formation. Splenic B-cells from Bcl6+/- Bach2+/- mice display accelerated plasmacytic differentiation and high expression of key plasma cell genes such as Prdm1, Xbp1 and CD138. ChIP-seq revealed that in B-cells BACH2 is mostly bound to genes together with its heterodimer partner MAFK. The BACH2-MAFK complex binds to sets of genes known to be involved in the GC response, 60% of which are also targets of BCL6. Approximately 30% of BACH2 peaks overlap with BCL6 including cis-regulatory sequences of the PRDM1 gene. BCL6 also modulates BACH2 protein stability and their protein levels are positively correlated in GC B-cells. Therefore, BCL6 and BACH2 cooperate to orchestrate gene expression patterning in GC B cells through both transcriptional and biochemical mechanisms, which collectively determine the proper initiation and timing of terminal differentiation. ChIP-seq using P18 antibodies in OCI-Ly7 cells

2013-11-17 | E-GEOD-47784 | biostudies-arrayexpress

A biochemical basis for toggling enhancers from the active to poised state in B cells

Project description:BCL6 is crucial for B-cell activation and lymphomagenesis. We used integrative genomics to explore BCL6 mechanism in normal and malignant B-cells. Surprisingly, BCL6 assembled distinct complexes at enhancers vs. promoters. At enhancers BCL6 preferentially recruited SMRT, which mediated H3K27 deacetylation through HDAC3, antagonized p300 activity and repressed transcription, but without decommissioning enhancers. This provides a biochemical basis for toggling enhancers from the active to poised state. Virtually all SMRT was bound with BCL6 suggesting that in B-cells BCL6 uniquely sequesters SMRT from other factors. In promoters BCL6 preferentially recruited BCOR, but most potently repressed promoters where it formed a distinctive ternary complex with SMRT and BCOR. Promoter repression was associated with decreased H3K36me3, H3K79me2 and Pol II elongation, linking BCL6 to transcriptional pausing. We identified the binding patterns of BCL6, SMRT, NCOR and BCOR corepressors in normal germinal center B cells and a DLBCL cell line (OCI-Ly1) using ChIP-seq. Additionally we treated lymphoma cells with siRNA against BCL6 and a non-targeted siRNA (NT control) and performed RNA-seq to identify the genes bound and repressed by BCL6. RNA-seq experiments were performed at 24h and 48h after siRNA treatments. Additional biological triplicate RNA-seq experiments were performed at 48h after BCL6 knockdown. Furthermore, a series of histone mark ChIP-seq and RNA polymerase ChIP-seq (total, Ser5-P and Ser2-P) were preformed to capture the chromatin states associated with the formation of BCL6 corepressor complexes.

2013-08-05 | E-GEOD-29282 | biostudies-arrayexpress

Effect of Bach2 overexpression in BCL6+/+ and -/- BCR-ABL1 transformed pre-B cells

Project description:The aim was to investigate how BCL6 genotype affects Bach2 dependent gene expression changes. We compared gene expression profiles of BCL6+/+ and BCL6-/- BCR-ABL1 transformed pre-B cells after inducible overexpression of Bach2.

2013-07-11 | E-GEOD-41042 | biostudies-arrayexpress

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

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

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.

2011-02-11 | E-GEOD-27074 | biostudies-arrayexpress

Flexible chromatin loops in the VH gene region of the Igh locus facilitate the generation of a diverse antibody repertoire

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

2013-09-30 | E-GEOD-43008 | biostudies-arrayexpress

Loop Extrusion Mediates Physiological Locus Contraction for V(D)J Recombination (3C-HTGTS)

Project description:Immunoglobulin heavy chain locus (Igh) VH, D, and JH gene segments are developmentally assembled into V(D)J exons. RAG endonuclease initiates V(D)J recombination by binding a JH-recombination signal sequence (RSS) within a chromatin-based recombination center (RC) and then, in an orientation-dependent process, scans upstream D-containing chromatin presented by cohesin-mediated loop extrusion for convergent D-RSSs to initiate DJH-RC formation. In primary pro-B cells, 100s of upstream VH-associated RSSs, embedded in convergent orientation to the DJH-RC-RSS, gain proximity to the DJH-RC for VH-to-DJH joining via a mechanistically-undefined VH-locus contraction process. Here, we report that a 2.4 mega-base VH locus inversion in primary pro-B cells nearly abrogates rearrangements of normally convergent VH-RSSs and cryptic RSSs, even though locus contraction per se is maintained. Moreover, this inversion activated rearrangement of both cryptic VH-locus RSSs normally in the opposite orientation and, unexpectedly, of normally-oriented cryptic RSSs within multiple, sequential upstream convergent-CBE domains. Primary pro-B cells had significantly reduced transcription of Wapl, a cohesin-unloading factor, versus levels in v-Abl pro-B lines that lack marked locus contraction or distal VH rearrangements. Correspondingly, Wapl depletion in v-Abl lines activated VH-locus contraction and orientation-specific RAG-scanning across the VH-locus. Our findings indicate that locus contraction and physiological VH-to-DJH joining both are regulated via circumvention of CBE scanning impediments.

2020-11-08 | GSE151909 | GEO

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2020-11-08 | GSE151908 | GEO

Loop Extrusion Mediates Physiological Locus Contraction for V(D)J Recombination (GRO-Seq)

2020-11-08 | GSE151907 | GEO