Project name: Homo sapiens

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 cellsOverall design: 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).

Data type: Other

Sample scope: Multiisolate

Relevance: Medical

Release date: 2010-05-12

Last updated: 2009-07-10