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Distinct SWI/SNF chromatin remodelling complexes act differentially to maintain stem-like exhausted CD8 T cells [RNA-seq]

ABSTRACT: Exhausted CD8 T cells (TEX) arise during chronic viral infections and cancer and limit disease control. Three major sequential epigenetic remodeling events occur as naïve CD8 T cells (TN) differentiate into TEX: initial activation, early bifurcation between effector (TEFF) and TEX precursors, and later differentiation of effector-like and terminal TEX subsets from progenitor TEX. The epigenetic factors mediating these transitions remain poorly understood. Here, we uncovered distinct roles for two versions of the SWI/SNF chromatin remodeling complex, BAF and PBAF, in TEX differentiation using in vivo CRISPR screening. Disruption of BAF ablated antigen-specific CD8 T cells early in chronic infection, suggesting a requirement for BAF-mediated remodeling in the early epigenetic remodeling events. In contrast, depletion of PBAF subunits enhanced TEX formation and promoted progenitor TEX differentiation into more differentiated TEX subsets by limiting accessibility of TCF-1 binding sites. Loss of PBAF improved tumor control alone and in combination with anti-PD-L1. Simultaneous depletion of BAF- and PBAF-specific subunits revealed that BAF is required for the beneficial impact of loss of PBAF on TEX differentiation. Thus, BAF and PBAF regulate epigenetic transitions in CD8 T cell differentiation, with PBAF acting at a later stage in exhaustion as a guardian to limit full TEX differentiation and preserve TEX progenitor populations with implications for cancer immunotherapy.

ORGANISM(S): Mus musculus

PROVIDER: GSE211410 | GEO | 2023/05/31

REPOSITORIES: GEO

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Distinct SWI/SNF chromatin remodelling complexes act differentially to maintain stem-like exhausted CD8 T cells [ATAC-seq]

Project description:Exhausted CD8 T cells (TEX) arise during chronic viral infections and cancer and limit disease control. Three major sequential epigenetic remodeling events occur as naïve CD8 T cells (TN) differentiate into TEX: initial activation, early bifurcation between effector (TEFF) and TEX precursors, and later differentiation of effector-like and terminal TEX subsets from progenitor TEX. The epigenetic factors mediating these transitions remain poorly understood. Here, we uncovered distinct roles for two versions of the SWI/SNF chromatin remodeling complex, BAF and PBAF, in TEX differentiation using in vivo CRISPR screening. Disruption of BAF ablated antigen-specific CD8 T cells early in chronic infection, suggesting a requirement for BAF-mediated remodeling in the early epigenetic remodeling events. In contrast, depletion of PBAF subunits enhanced TEX formation and promoted progenitor TEX differentiation into more differentiated TEX subsets by limiting accessibility of TCF-1 binding sites. Loss of PBAF improved tumor control alone and in combination with anti-PD-L1. Simultaneous depletion of BAF- and PBAF-specific subunits revealed that BAF is required for the beneficial impact of loss of PBAF on TEX differentiation. Thus, BAF and PBAF regulate epigenetic transitions in CD8 T cell differentiation, with PBAF acting at a later stage in exhaustion as a guardian to limit full TEX differentiation and preserve TEX progenitor populations with implications for cancer immunotherapy.

2023-05-31 | GSE211409 | GEO

Decitabine-induced T cell remodeling facilitates a high antitumor response to PD-1 blockade therapy by promoting the expansion and effector function of CD8+ progenitor exhausted T cells

Project description:CD8+ exhausted T (Tex) cells are heterogeneous with distinct transcriptional and epigenetic landscapes. PD-1 inhibitors reinvigorate progenitor Tex cells, which subsequently differentiate into irresponsive terminal Tex cells and impair the longlasting antitumor response of PD-1 blockade therapy. How to maintain durable proliferative capacity of progenitor Tex cells is important but remains largely unknown. Here, we showed that low-dose DNA demethylating agent decitabine-pretreated CD8+ progenitor Tex cells had enhanced cytolytic activity against tumors after anti-PD-1 treatment in vitro and could not reactivate the terminal Tex cells. Decitabine-plus-anti-PD-1 treatment promoted the activation and expansion of endogenous tumor-infiltrated CD8+ progenitor Tex cells and efficiently suppressed tumor growth in multiple mice tumor models. The single-cell RNA-sequencing, TCR-sequencing and ATAC-sequencing demonstrated that decitabine-plus-anti-PD-1 combination altered the transcriptional and epigenetic status of CD8+ Tex cells and markedly elevated the clonally expansion and effector function of progenitor Tex cells as compared with anti-PD-1 monotherapy, presenting increased expression of genes associated with T cell activation, proliferation, cytolytic activity, memory and mitochondrial metabolism. Strikingly, decitabine-plus-anti-PD-1 combination sustained the expression and activity of AP-1 transcription factor JunD, which was reduced following PD-1 blockade therapy. Suppressing JNK/AP-1 signaling in CD8+ T cells blunted decitabine-plus-anti-PD-1-induced activation of CD8+ T cells. Together, our findings show that the epigenetic therapy remodels CD8+ progenitor Tex subset, improves responsiveness to anti-PD-1 therapy and suppresses CD8+ T cell terminal differentiation.

2022-07-28 | GSE209965 | GEO

Structure of nucleosome-bound human PBAF complex

Project description:BAF and PBAF are mammalian SWI/SNF family chromatin remodeling complexes that possess multiple histone/DNA-binding subunits and create nucleosome-depleted/free regions for transcription activation. Despite previous structural studies and recent advance of SWI/SNF family complexes, it remains incompletely understood how PBAF-nucleosome complex is organized. Here we determined structure of 13-subunit human PBAF in complex with acetylated nucleosome in ADP-BeF3-bound state. Four PBAF-specific subunits work together with nine BAF/PBAF-shared subunits to generate PBAF-specific modular organization, distinct from that of BAF at various regions. PBAF-nucleosome structure reveals six histone-binding domains and four DNA-binding domains/modules, the majority of which directly bind histone/DNA. This multivalent nucleosome-binding pattern, not observed in previous studies, suggests that PBAF may integrate comprehensive chromatin information to target genomic loci for function. Our study reveals molecular organization of subunits and histone/DNA-binding domains/modules in PBAF-nucleosome complex and provides structural insights into PBAF-mediated nucleosome association complimentary to the recently reported PBAF-nucleosome structure.

2023-03-11 | PXD036708 | Pride

Different SWI/SNF complexes coordinately promote R-loop- and RAD52- dependent transcription-coupled homologous recombination

Project description:The SWI/SNF family of ATP-dependent chromatin remodeling complexes are implicated in multiple DNA damage response mechanisms and frequently mutated in cancer. The BAF and PBAF complexes are two major types of SWI/SNF complexes that are functionally distinguished by their exclusive subunits. Accumulating evidence suggests that double-strand breaks (DSBs) in transcriptionally active DNA are preferentially repaired by a dedicated homologous recombination pathway. We show that different BAF and PBAF subunits promote homologous recombination and are rapidly recruited to DSBs in a transcription-dependent manner. The PBAF complex promotes RNA polymerase II eviction near DNA damage to rapidly initiate transcriptional silencing, while the BAF complex helps to maintain this transcriptional silencing. Furthermore, ARID1A-containing BAF complexes promote RNaseH1 and RAD52 recruitment to facilitate R-loop resolution and DNA repair. Our results highlight how multiple SWI/SNF complexes perform different functions to enable DNA repair in the context of actively transcribed genes.

2023-07-31 | PXD035140 | Pride

Brd7, a novel PBAF-specific SWI/SNF subunit, is required for gene activation and repression in embryonic stem cells

Project description:The composition of chromatin remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. Here, we investigate the composition of SWI/SNF complexes in embryonic stem cells (ESCs). In contrast to differentiated cells, ESCs have a biased incorporation of certain paralogous SWI/SNF subunits, with low levels of Brm, BAF170 and ARID1B. Upon differentiation, the expression of these subunits increases, resulting in a higher diversity of compositionally distinct SWI/SNF enzymes. We also identify Brd7 as a novel component of the PBAF complex in both ESCs and differentiated cells. Using shRNA-mediated depletion of Brg1, we show that SWI/SNF can function as both a repressor and an activator in pluripotent cells, regulating expression of developmental modifiers and signaling components such as Nodal, ADAMTS1, Bmi-1, CRABP1 and TRH. Knock-down studies of PBAF-specific Brd7 and of a signature subunit within the BAF complex, ARID1A, show that these two sub-complexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally, we examine the role of SWI/SNF in regulating its target genes during differentiation. We find that SWI/SNF affects recruitment of components of the pre-initiation complex in a promoter-specific manner, to modulate transcription positively or negatively. Taken together, our results provide insight into the function of compositionally diverse SWI/SNF enzymes that underlie their inherent gene-specific mode of action. R1 ESCs were infected in duplicates with shRNA targeting Brg1 or GLUT4 (as a control). Knockdown of Brg1 mRNA affected Brg1 protein levels efficiently. RNA was isolated 67 hours post-infection and analyzed using microarrays.

2010-03-04 | E-GEOD-7791 | biostudies-arrayexpress

Loss of PBAF Promotes Effector Differentiation and Limits CD8+ T Cell Exhaustion in Chronic Viral Infection and Cancer [multiomics]

Project description:To gain insights into how PBAF complex regulates dynamic chromatin structure changes in LCMV-specific CD8+ T cells during chronic viral infection and examine the how PBAF-deficiency alters the transcriptional and epigenetic heterogeneity of CD8+ T cells, we performed single cell RNA + ATAC multiomic sequencing on Arid2- and Pbrm1-deficient CD8+ T cells and their wild-type counterpart.

2023-06-22 | GSE222346 | GEO

A non-canonical BRD9-containing BAF chromatin remodeling complex regulates naïve pluripotency in mouse embryonic stem cells

Project description:The mammalian BRG1-associated factors (BAF) complex is a multi-subunit chromatin remodeling complex that is an important component of the embryonic stem cell (ESC) transcriptional regulatory network. However, the role of individual subunits in BAF complex targeting and function needs to be elucidated. Here, we find that the Bromodomain containing protein 9 (BRD9) defines a smaller, non-canonical BAF complex in mouse ESCs that is distinct from the canonical embryonic stem cell BAF (esBAF) and the polybromo-associated BAF (PBAF) complexes. This BRD9-containing BAF complex, or BBAF complex, uniquely incorporates the BRD4-interacting chromatin remodeling associated protein-like (BICRAL) or its paralog BICRA and lacks several esBAF subunits including BAF47, ARID1A and BAF57. We demonstrate that BBAF and esBAF complexes are targeted to different features of the genome and are co-bound with different sets of pluripotency transcription factors. Specifically, BBAF complexes co-localize with key regulators of naïve pluripotency, KLF4 and Sp5, on the genome. Consistent with this, we provide evidence that BBAF’s specific function is to regulate the transcription of genes involved in the maintenance of naïve pluripotency, including Nanog and Prdm14. Additionally, we show that BRD9 is displaced from chromatin by the selective BRD9 bromodomain inhibitor, I-BRD9, and that this leads to changes in target gene expression. Together, our results provide evidence for the identification of a new BAF complex, and demonstrate functionally specific roles for BAF complex assemblies in maintaining the transcriptional network of pluripotency.

2018-10-18 | PXD010670 | Pride

The BAF complex blocks Myogenesis in rhabdomyosarcoma

Project description:Rhabdomyosarcoma (RMS) is a highly malignant pediatric cancer of skeletal muscle lineage. The aggressive alveolar subtype is commonly characterized by t(2;13) or t(1;13) translocations with the expression of PAX3- or PAX7-FOXO1 fusion transcription factors respectively and is known as fusion positive RMS (FP-RMS). FP-RMS tumors rely on the fusion gene to maintain their proliferative state while avoiding terminal differentiation program. Since disruptions of normal development are likely governed by epigenetic changes in these low-mutational-burden tumors, we investigated the contributions of chromatin regulatory complexes to RMS tumor maintenance. We demonstrate the essentiality of the mSWI/SNF ATPase BRG1 for FP-RMS proliferation and discover that RMS significantly overexpress SMARCA4 (encoding BRG1) compared to skeletal muscle. We define the mSWI/SNF subunit repertoire in FP-RMS and provide evidence for the assembly of multiple mSWI/SNF complexes including canonical BAF, PBAF and non-canonical (nc)BAF in FP-RMS. Proteomic studies suggest proximity between PAX3-FOXO1 and BAF complexes, which was further supported by genome-wide binding profiles revealing enhancer colocalization of BAF with FP-RMS core regulatory transcription factors. We report that mSWI/SNF complexes act as sensors of chromatin state, which are recruited to sites of de novo histone acetylation. Phenotypically, interference with mSWI/SNF complex function induces transcriptional activation of the skeletal muscle differentiation program associated with MYCN enhancer invasion at myogenic target genes. Finally, BRG1 targeting compounds reproduce the effects of genetic ablation. We conclude that inhibition of BRG1 overcomes the differentiation blockade of FP-RMS cells and may provide a therapeutic strategy for treating this lethal childhood tumor.

2020-11-20 | MSV000086494 | MassIVE

SMARCA4 Rescue Profiling [ChIP]

Project description:Mutations in SMARCA4, a central ATPase of the human BAF/PBAF chromatin remodeling complexes, cause developmental abnormalities and promote cancer development. The pathogenic effects of SMARCA4 loss are often linked to the de-regulation of a relatively small number of key target genes. Here, to understand how chromatin remodeling by SMARCA4 results in specific transcriptional perturbations, we used genome engineering to correct a homozygous mutation in SMARCA4 in the well-characterized lung adenocarcinoma A549 cell line and profiled changes in SMARCA2/4 occupancy, chromatin accessibility, histone marks and transcription. Restoration of SMARCA4 causes a dramatic increase in chromatin accessibility at low affinity TF binding sites. Despite the widespread increase in chromatin accessibility, we observe comparatively attenuated changes in gene expression. Although there is a marked correlation between the number of local activated DHSs and the transcriptional responsivity of a gene, the influence of distal DHSs appears modified by a gene's promoter architecture and domain-scale chromatin organization. The largest changes in expression occur for genes in isolated, SMARCA4 sensitive chromatin domains that undergo region-wide chromatin remodeling upon reintroduction of SMARCA4. Our results reveal that interactions between distal enhancers, genome organization, and promoter architecture add transcriptional specificity to the global chromatin effects of BAF/PBAF complex perturbation and target the response to key developmental pathways.

2020-05-20 | GSE132290 | GEO

SMARCA4 Rescue Profiling [Dnase]

2020-05-20 | GSE132292 | GEO

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