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Splenic CD43- B cells exhibit DNA hypomethylation specifically at repetitive elements compared to CD43+ cells

ABSTRACT: EZH2 is a histone methyltransferase that deposits H3K27me2/3 in heterochromatin and it is misregulated in tumorigenesis. Inhibition of heterochromatin can induce viral mimicry in cancer cells, where upregulated repetitive elements are detected by cytosolic pattern recognition receptors (PRRs) to activate inflammatory signaling. Here we demonstrate that EZH2 inhibitors stimulate inflammation and immune self-recognition of resting splenic B cells. We generated a PRR loss-of-function mouse model called RIC with mutations in Rigi, Ifih1 (MDA5), and Cgas. In both WT and RIC mutant B cells, EZH2 inhibition caused loss of H3K27me3 at repetitive elements and upregulated their expression. However, expression of inflammatory chemokines in B cells was interrupted by the RIC mutations. Furthermore, recruitment of cytotoxic T cells and neutrophils in response to EZH2 inhibition was blocked in RIC mutants preserving viability of B cells. This study demonstrates a pharmacologically induced mechanism of inflammation that causes self-recognition and B cell death.

ORGANISM(S): Mus musculus

PROVIDER: GSE229684 | GEO | 2023/10/18

REPOSITORIES: GEO

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Project description:DNA double strand breaks (DSBs) in repetitive sequences are a potent source of genomic instability, due to the possibility of non-allelic homologous recombination (NAHR). Repetitive sequences are especially at risk during meiosis, when numerous programmed DSBs are introduced into the genome to initiate meiotic recombination 1. Within the budding yeast repetitive ribosomal (r)DNA array, meiotic DSB formation is prevented in part through Sir2-dependent heterochromatin 2,3. Here, we demonstrate that the edges of the rDNA array are exceptionally susceptible to meiotic DSBs, revealing an inherent heterogeneity within the rDNA array. We find that this localised DSB susceptibility necessitates a border-specific protection system consisting of the meiotic ATPase Pch2 and the origin recognition complex subunit Orc1. Upon disruption of these factors, DSB formation and recombination specifically increased in the outermost rDNA repeats, leading to NAHR and rDNA instability. Strikingly, the Sir2-dependent heterochromatin of the rDNA itself was responsible for the induction of DSBs at the rDNA borders in pch2? cells. Thus, while Sir2 activity globally prevents meiotic DSBs within the rDNA, it creates a highly permissive environment for DSB formation at the heterochromatin/euchromatin junctions. Heterochromatinised repetitive DNA arrays are abundantly present in most eukaryotic genomes. Our data define the borders of such chromatin domains as distinct high-risk regions for meiotic NAHR, whose protection may be a universal requirement to prevent meiotic genome rearrangements associated with genomic diseases and birth defects. This SuperSeries is composed of the following subset Series: GSE30071: ssDNA mapping in dmc1 strains GSE30072: ChIP-chip of DSB factors in wild type and pch2 strains Two types of study were undertaken to understand the regulation of meiotic DSB formation close to repetitive DNA elements in yeast. First, DSBs were mapped using ssDNA enrichment in strains isogenic for a dmc1 mutation, and also including pch2 delete, orc1-161, rdna delete and a reciprocal translocation between chromosomes 2 and 12 (trans2to12). Second, the association of the DSB factors Hop1, Rec114, Mer2, and Mre1, as well as total histone H3 and H3K4-trimethylation were measured by ChIP-chip analysis in wild-type and pch2 delete strains.

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Splenic CD43- B cells exhibit DNA hypomethylation specifically at repetitive elements compared to CD43+ cells

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