Dataset Information

DAXX-ATRX-H3.3 Regulation of p53 Chromatin Binding and DNA Damage Response [ChIP-Seq]

ABSTRACT: DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.

ORGANISM(S): Homo sapiens

PROVIDER: GSE186442 | GEO | 2022/07/19

REPOSITORIES: GEO

ACCESS DATA

Similar Datasets

Project description:Objective: Daxx is a protein with multiple functions and is essential for embryonic development. Daxx knockout embryos fail to develop properly and exhibit lethal phenotype around E6.5. One of the important functions is as a histone chaperone for the histone H3 variant, H3.3. Daxx interacts with Atrx to form a protein complex that deposits H3.3 into heterochromatic regions of the genome, including centromeres, telomeres and repeat loci. Here, we investigated how histone chaperone function of Daxx contributes to the embryonic development. Methods: We developed two Daxx mutant alleles in the mouse germline which abolish the interactions between Daxx and Atrx (DaxxY130A), Daxx and H3.3 (DaxxS226A). We set up mating between either heterozygous DaxxY130A or heterozygous DaxxS226A individually and looked for the viability of homozygous mutants at different development stages. We also performed bulk RNA-seq on tissues from the two mutant embryos and analyzed the changes in gene expression and transposable elements (TE). Results: We found that the interaction between Daxx and Atrx is dispensable for viability in both the pre- and post-natal setting as homozygous Daxx-Y130A mutants are both viable and fertile. The loss of the Atrx interaction, however, does cause dysregulated expression of both endogenous retroviruses and nearby protein coding genes. On the contrary, the interaction between Daxx and H3.3 is not required for embryonic development but is essential for postnatal viability. Transcriptome analysis of embryonic tissues demonstrates that this interaction is important for silencing endogenous retroviruses and for maintaining proper hematopoiesis. Conclusions: The histone chaperone function of Daxx is dispensable for embryonic development but important for hematopoiesis, which is independent of the interaction with Atrx. Moreover, both the interactions with Atrx and with H3.3 is important for regulation of ERV expression. Overall, these results clearly demonstrate that Daxx and H3.3 have both Atrx-dependent and independent functions, advancing our understanding of this epigenetic regulatory complex.

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.

Dataset Information

DAXX-ATRX-H3.3 Regulation of p53 Chromatin Binding and DNA Damage Response [ChIP-Seq]

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure