Dataset Information

A Genome-wide CRISPR Screen Reveals a Role for the Non-canonical Nucleosome-Remodeling BAF Complex in Foxp3 Expression and Regulatory T Cell Function.

ABSTRACT: Regulatory T (Treg) cells play a pivotal role in suppressing auto-reactive T cells and maintaining immune homeostasis. Treg cell development and function are dependent on the transcription factor Foxp3. Here, we performed a genome-wide CRISPR loss-of-function screen to identify Foxp3 regulators in mouse primary Treg cells. Foxp3 regulators were enriched in genes encoding subunits of the SWI/SNF nucleosome-remodeling and SAGA chromatin-modifying complexes. Among the three SWI/SNF-related complexes, the Brd9-containing non-canonical (nc) BAF complex promoted Foxp3 expression, whereas the PBAF complex was repressive. Chemical-induced degradation of Brd9 led to reduced Foxp3 expression and reduced Treg cell function in vitro. Brd9 ablation compromised Treg cell function in inflammatory disease and tumor immunity in vivo. Furthermore, Brd9 promoted Foxp3 binding and expression of a subset of Foxp3 target genes. Our findings provide an unbiased analysis of the genetic networks regulating Foxp3 and reveal ncBAF as a target for therapeutic manipulation of Treg cell function.

SUBMITTER: Loo CS

PROVIDER: S-EPMC7341821 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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A Genome-wide CRISPR Screen Reveals a Role for the Non-canonical Nucleosome-Remodeling BAF Complex in Foxp3 Expression and Regulatory T Cell Function.

Loo Chin-San CS Gatchalian Jovylyn J Liang Yuqiong Y Leblanc Mathias M Xie Mingjun M Ho Josephine J Venkatraghavan Bhargav B Hargreaves Diana C DC Zheng Ye Y

Immunity 20200707 1

Regulatory T (Treg) cells play a pivotal role in suppressing auto-reactive T cells and maintaining immune homeostasis. Treg cell development and function are dependent on the transcription factor Foxp3. Here, we performed a genome-wide CRISPR loss-of-function screen to identify Foxp3 regulators in mouse primary Treg cells. Foxp3 regulators were enriched in genes encoding subunits of the SWI/SNF nucleosome-remodeling and SAGA chromatin-modifying complexes. Among the three SWI/SNF-related complexe ...[more]

PMID: 32640256

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Project description:Human and mouse somatic cells can be reprogrammed by the combination of Oct4, Sox2, Klf4, and c-Myc, but the efficiency of reprogramming is low. To better understand the process of reprogramming we sought to identify factors that mediate reprogramming at higher efficiency. For this we established an assay to screen nuclear fractions from the extracts of pluripotent cells based on Oct4 reactivation. We identified components of the ATP-dependent SWI/SNF chromatin-remodeling complex, which when used along with the above four factors increase reprogramming efficiency by five-fold and improve the quality of the reprogrammed cells. These cells were found to be capable of germline transmission and exhibited pluripotency according to gene expression and in vivo and in vitro assays. SWI/SNF was found to replace c-Myc and mediate its effects by facilitating recruitment of Oct4 on target promoters during reprogramming. Thus, somatic cell reprogramming using chromatin-remodeling molecules represents an efficient method of generating reprogrammed cells. DNA-free RNA samples to be hybridized on Illumina expression BeadChips were processed using a linear amplification kit (Ambion) (generating IVT duration: 12h). cRNA samples were quality-checked on a 2100 Bioanalyzer (Agilent) and hybridized as biological triplicates onto MouseWG-6 V2 chips as recommended and using materials / reagents provided by the manufacturer (hybridization time: 18h). The Myc probe on the V2 arrays was found to be defective. The bead intensities were mapped to gene information using BeadStudio 3.2 (Illumina), background correction was performed using the Affymetrix Robust Multi-array Analysis (RMA) background correction model, variance stabilization was performed using log2 scaling, and gene expression normalization was calculated with the quantile method implemented in the lumi package of R-Bioconductor. Data post-processing and graphics were performed with in-house developed functions in Matlab. Hierarchical clusters of genes and samples were performed with a one minus correlation metric and the average (unweighted pair group) linkage method. 4 samples were analyzed, each one them by triplicate. ESC: Mouse Embryonic Stem Cells (OG2 mix female and male) MEF: Mouse Embryonic Fibroblasts (OG2 male) iPS4F: Mouse induced Pluripotent Stem cells with 4 factors (Oct4, Sox2, Klf4, c-myc) iPS6F: Mouse induced Pluripotent Stem cells with 6 factors (Oct4, Sox2, Klf4, c-myc, Brg1, Baf155)

Project description:Persistence of a reservoir of latently infected memory T cells provides a barrier to HIV eradication in treated patients. Several reports have implicated the involvement of SWI/SNF chromatin remodeling complexes in restricting early steps in HIV infection, in coupling the processes of integration and remodeling, and in promoter/LTR transcription activation and repression. However, the mechanism behind the seemingly contradictory involvement of SWI/SNF in the HIV life cycle remains unclear. Here we addressed the role of SWI/SNF in regulation of the latent HIV LTR before and after transcriptional activation. We determined the predicted nucleosome affinity of the LTR sequence and found a striking reverse correlation when compared to the strictly positioned in vivo LTR nucleosomal structure; sequences encompassing the DNase hypersensitive regions displayed the highest nucleosome affinity, while the strictly positioned nucleosomes displayed lower affinity for nucleosome formation. To examine the mechanism behind this reverse correlation, we used a combinatorial approach to determine DNA accessibility, histone occupancy, and the unique recruitment and requirement of BAF and PBAF, two functionally distinct subclasses of SWI/SNF at the LTR of HIV-infected cells before and after activation. We find that establishment and maintenance of HIV latency requires BAF, which removes a preferred nucleosome from DHS1 to position the repressive nucleosome-1 over energetically sub-optimal sequences. Depletion of BAF resulted in de-repression of HIV latency concomitant with a dramatic alteration in the LTR nucleosome profile as determined by high resolution MNase nucleosomal mapping. Upon activation, BAF was lost from the HIV promoter, while PBAF was selectively recruited by acetylated Tat to facilitate LTR transcription. Thus BAF and PBAF, recruited during different stages of the HIV life cycle, display opposing function on the HIV promoter. Our data point to the ATP-dependent BRG1 component of BAF as a putative therapeutic target to deplete the latent reservoir in patients.

Dataset Information

A Genome-wide CRISPR Screen Reveals a Role for the Non-canonical Nucleosome-Remodeling BAF Complex in Foxp3 Expression and Regulatory T Cell Function.

Publications

A Genome-wide CRISPR Screen Reveals a Role for the Non-canonical Nucleosome-Remodeling BAF Complex in Foxp3 Expression and Regulatory T Cell Function.

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