Histone H3.3 is a replication-independent histone variant, which replaces histones that are turned over throughout the entire cell cycle. H3.3 deposition at euchromatin is dependent on HIRA, whereas ATRX/Daxx deposits H3.3 at pericentric heterochromatin and telomeres. The role of H3.3 at heterochromatic regions is unknown, but mutations in the ATRX/Daxx/H3.3 pathway are linked to aberrant telomere lengthening in certain cancers. In this study, we show that ATRX-dependent deposition of H3.3 is no ...[more]
Project description:Regions of chromatin modified by H3K4me1 and H3K4me3 were identified in mouse erythroid cells using ChIP-seq. Chip-seq experiements were performed in C57bl\6 mouse erythroid Ter119+ cells.
Project description:Analysis of gene expression in WT and ATRX KO Cast x 129 Mouse ES cells Paired end RNA-seq analysis of PolyA selected RNA and PolyA depeleted RNA from in both wildtype nd ATRX knocked out Castx129 Mouse ES Cells
Project description:Regions bound by the erythroid transcription factors GATA1 and NFE2 and the general factor CTCF were identified in mouse erythroid cells using ChIP-seq. Chip-seq experiements were performed in mouse erythroid Ter119+ cells.
Project description:In mammals, DNA methylation is essential for protecting repetitive sequences from aberrant transcription, translocation, and homologous recombination. However, DNA hypomethylation occurs during specific developmental stages (e.g. preimplantation embryos) and in certain cell types (e.g., primordial germ cells). The absence of dysregulated repetitive elements in these cells suggests the existence of alternative mechanisms that prevent genome instability triggered by DNA hypomethylation. In this report, we seek to elucidate the factors that play a critical role in ensuring genome stability by focusing on DAXX and ATRX, two proteins that have been linked to transcriptional control and epigenetic regulation. We carried out ChIP-seq and RNA-seq analyses to compare the genome-wide binding and transcriptome profiles of DAXX and ATRX in mouse ES (mES) cells triple knocked out for the three mammalian DNA methyltransferases (DNMTs) (TKO cells) to those in wildtype mES cells. Our data indicate that DAXX and ATRX are distinct in their chromatin-binding profiles and highly co-enriched at tandem repetitive elements. Global DNA hypomethylation, as was the case in TKO cells, further promoted the recruitment of the DAXX/ATRX complex to tandem repeat sequences including IAP (intracisternal A‐particle) retrotransposons and telomeres. Inhibition of DAXX or ATRX in cells with hypomethylated genomes (e.g., TKO cells, mES cells cultured in ground-state conditions, and preimplantation embryos) increased aberrant transcriptional de-repression of repeat elements and dysfunction at telomeres. Furthermore, we provide evidence that DAXX/ATRX-dependent silencing may occur through DAXX’s interaction with SUV39H1 and increased H3K9me3 on repetitive sequences. Our study suggests that DAXX and ATRX are important for safeguarding the genome, particularly in silencing repetitive elements in the absence of DNA methylation. We tested the hypothesis that the DAXX/ATRX complex participates in protecting repetitive elements in the absence of DNA methylation. To this end, we investigated genome-wide chromatin targeting of DAXX and ATRX in wildtype mES cells, and in mES cells that exhibit extensive loss of DNA methylation due to homozygous knockout of all three DNA.
Project description:ATRX is a severe X-linked disorder characterized by mental retardation, facial dysmorphism, urogenital abnormalities and alpha-thalassemia. The disease is caused by mutations in ATRX gene, which encodes a protein belonging to the SWI/SNF DNA helicase family, a group of proteins involved in the regulation of gene transcription at the chromatin level. In order to identify specific genes involved in the pathogenesis of the disease, we compared, by cDNA microarray, the expression levels of approximately 8500 transcripts between ATRX and normal males of comparable age. The analysis has been performed on pooled RNA extracted by Peripheral blood mononuclear cell pellet of three male ATRX patients in comparison to that obtained from a pool of 42 normal males (age 7.6+ 2.4).
Project description:ATRX is a member of the SWI2/SNF2 family of chromatin remodeling proteins and primarily functions at heterochromatic loci via its recognition of ‘repressive’ histone modifications (e.g., H3K9me3). Despite significant roles for ATRX during normal neural development, as well as its relationship to human disease, ATRX function in the central nervous system is not well understood. Here, we describe ATRX’s ability to recognize an activity-dependent combinatorial histone modification, H3K9me3S10ph, in post-mitotic neurons. In neurons, this “methyl/phos” switch occurs exclusively following periods of stimulation and is highly enriched at heterochromatic repeats associated with centromeres. Using a multifaceted approach, we reveal that H3K9me3S10ph bound Atrx represses non-coding transcription of centromeric minor satellite sequences during instances of heightened activity. Our results indicate an essential interaction between ATRX and a previously uncharacterized histone modification in the central nervous system and suggest a potential role for abnormal repetitive element transcription in pathological states manifested by ATRX dysfunction. For Atrx ChIP-seq, IPs were performed on three control vs. three KCl stimulated (all representing biological, and not technical replicates) primary cultured mouse cortical neurons at DIV 8. All samples were normalized to background input levels. For H3K9me3S10phos ChIP-seq, biological singlecates (control vs. forskolin) were analyzed against respective inputs.
Project description:The histone variant macroH2A generally associates with transcriptionally inert chromatin, however the factors that regulate its chromatin incorporation remain elusive. Here, we identify the SWI/SNF helicase, ATRX, as a novel macroH2A interacting protein. Unlike its role in assisting H3.3 chromatin deposition, ATRX acts as a negative regulator of macroH2A’s chromatin association. In human erythroleukemic cells deficient for ATRX, ChIP-sequencing studies reveal that macroH2A accumulates at the HBA gene cluster on the subtelomere of chromosome 16, coinciding with the loss of α globin expression. Collectively, our results implicate deregulation of macroH2A’s distribution as a contributing factor to the α thalassemia phenotype of ATRX syndrome. Mononucleosomes from K562 cells bearing integrated lentiviral shRNA constructs targeting either luciferase (shluc) or ATRX (sh92) were isolated and ChIP'd with mH2A1 antibody. DNA from shluc Input and the two mH2A1 ChIPs were isolated and sequenced on Illumina's Hiseq.