Shown is a generic euchromatic Arabidopsis thaliana gene in the context of chromatin modifications known to affect gene expression. Relevant gene regions are indicated. Histone octamers are shown as purple cylinders. The histone variant H2A.Z incorporated by the SWR1 chromatin remodeling complex[75–77] is shown as a green ellipse. The promoter is partially depleted of nucleosomes, which is observed in many constitutively expressed genes and in inducible genes after the combined activity of chromatin remodeling ATPases and histone modifiers. Above the graphic grey shading indicates the promoter region, the 5′ end of the gene, the central gene region, the 3′ end of the gene, and the 3′ intergenic region. The spatial distribution of covalent histone modifications is indicated relative to these five regions. Modifications for which distribution was determined by global binding studies are indicated in bold[1,11,47,48,50], to distinguish them from those for which information is only available from studies of a limited number of genes (see Table 2 for examples). Note that H3K27me3 and H3K9me3 do not overlap, genes repressed by H3K27me3 are devoid of H3K9me3 and vice versa[11]. Spatial distribution of DNA methylation and of the Heterochromatin Protein 1 homolog LHP1/TFL2, two other chromatin regulators whose distribution was mapped genome-wide, is also indicated.
¹ H3K9me3 and H3K36me2 may have different roles on transcription dependent on their location[3].