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ATRX - a chromatin remodelling protein interactome

ABSTRACT: ATRX is a chromatin remodelling protein of the SWI/SNF family, mutations in which cause alpha thalassemia X-linked (ATRX) intellectual disability syndrome and are highly associated with a number of cancers characterized by alternative lengthening of telomeres. ATRX functions with the histone chaperone DAXX to facilitate deposition of the histone variant H3.3 at heterochromatic regions such as telomere and pericentric repeats, resulting in a unique form of heterochromatin characterized by both trimethylation of histone H3 at lysine 9 (H3K9me3) and H3.3. How ATRX is recruited to these regions remain unclear.To better understand it, we therefore used immunoprecipitation-coupled to mass spectrometry (IP-MS) to identify potential factors that interact with ATRX and may promote its localization and function. Based on our proteomics results, we identified known ATRX-interacting proteins, DAXX and MRE11. We also identified a number of proteins that have been genetically linked to G-quadruplex structures. Interestingly, we identified members of DNA replcation machinery MCM complex (e.g. MCM2, MCM4, MCM6, and MCM7) and the faciliates chromatin transcription (FACT) comeplex as novel ATRX-interacting proteins. We then verified the interaction of ATRX to MCM proteins and FACT subunits by co-immunoprecipition/immunoblot and proximity ligation assay.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Laura Banaszynski

PROVIDER: MSV000085543 | MassIVE | Wed Jun 03 14:01:00 BST 2020

REPOSITORIES: MassIVE

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Project description:Epigenetic environment of histone H3.3 on promoters revealed by integration of imaging and genome-scale chromatin and methyl-DNA immunoprecipitation information. Chromatin regions with different transcriptional outputs are distinguished by the deposition of histone variants. Histone H3.3 is incorporated into chromatin in a replication-independent manner; yet the relationship between H3.3 deposition, chromatin environment is incompletely understood. We have integrated imaging and genome-scale chromatin and methyl-DNA immunoprecipitation approaches to investigate the genomic distribution of epitope-tagged H3.3 in relation to histone modifications, DNA methylation and transcription. Results: Imaging shows that H3.3, in contrast to replicative H3.1 or H2B, is enriched in chromatin marked by histone modifications of active genes. A genome-wide survey identifies 1,649 H3.3-enriched promoters, only a subset of which is co-enriched in H3K4me3, H3K9me3 and/or H3K27me3, with a preference for H3K4me3, corroborating imaging data. H3.3-enriched promoters are depleted of H3.3 at the TSS in a transcription-independent manner. H3.3 is found predominantly on CpG-rich unmethylated promoters, creating a condition favourable for transcription. In undifferentiated mesenchymal stem cells, H3.3 target genes are linked to signaling and mesodermal differentiation, suggesting that H3.3 may be a mark of lineage priming. Conclusions: A minor fraction of H3.3 is targeted to promoters, which are predominantly CpG-rich, DNA unmethylated and devoid of detectable trimethylated H3K4, K9 and K27. Among H3.3 target promoters co-marked by methylated H3, H4K4me3 is preferred, with or without H3K27me3, arguing that in mesenchymal stem cells H3.3 marks transcriptionally active or potentially active promoters. Key words: Imaging, ChIP-chip, MeDIP-chip, histone H3.3, mesenchymal stem cells ChIP-chip and MeDIP-chip experiments: Performed with two independent biological replicates. Gene expression profiling experiments: Total RNA obtained from H3.3-EGFP transfected or empty-EGFP transfected mesenchymal stem cells compared to untransfected mesenchymal stem cells. Raw expression data linked below as supplementary file (GSE17053_Illumina_non-normalized_data.txt).

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ATRX - a chromatin remodelling protein interactome

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