GSE160408
Linker histones mediate sequence-specific regulation of chromosomal organization and H3K27me3 enrichment over genes and telomeric repeats (ATAC-Seq)
Chromatin architecture relies on histone H1 whose central globular domain (GH1) sits on the nucleosome dyad and carboxy-terminal domain associates with linker DNA. We report that Arabidopsis H1 positively influences H3K27me3 chromatin enrichment over protein-coding genes but oppositely prevents its accumulation on telomeres and heterochromatic Interstitial Telomeric Repeats (ITRs). Contrasting with their neighboring heterochromatic environment, pericentromeric ITR regions remain highly compacted and are more prone to long-distance interactions with telomeres in H1 mutant plants. The switch from H1-rich to H3K27me3-rich ITR chromatin is further accompanied by an invasion of GH1-Myb Telomeric Repeat Binding protein 1 (TRB1), a structural component of telomeres capable to trigger H3K27me3 deposition over protein-coding genes displaying short telomeric motifs. This dual effect led us to propose a competition mechanism between H1 and TRB that prevents massive H3K27me3 deposition over large blocks of repeated motifs, thereby contributing to regulate H3K27me3 homeostasis over the genome. Overall design: Examination of chromatin accessibility in WT and 2h1 plants by ATAC-seq.