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Review
. 2017 Apr:43:31-37.
doi: 10.1016/j.gde.2016.11.001. Epub 2016 Dec 8.

H3K27 methylation: a promiscuous repressive chromatin mark

Elizabeth T Wiles  1 , Eric U Selker  2
Affiliations
Review

H3K27 methylation: a promiscuous repressive chromatin mark

Elizabeth T Wiles et al. Curr Opin Genet Dev. 2017 Apr.

Abstract

Polycomb Repressive Complex 2 (PRC2) is a multiprotein complex that catalyzes the methylation of lysine 27 on histone H3 (H3K27me). This histone modification is a feature of facultative heterochromatin in many eukaryotes and maintains transcriptional repression established during early development. Understanding how PRC2 targets regions of the genome to be methylated remains poorly understood. Different cell types can show disparate patterns of H3K27me, and chromatin perturbations, such as loss of marks of constitutive heterochromatin, can cause redistribution of H3K27me, implying that DNA sequence, per se, is not sufficient to define the distribution of this mark. Emerging information supports the idea that the chromatin context-including histone modifications, DNA methylation, transcription, chromatin structure and organization within the nucleus-informs PRC2 target selection.

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Figures

Figure 1
Figure 1. Model in which PRC2 responds to the chromatin environment to establish H3K27me domains
Repressive features of constitutive heterochromatin including DNA methylation (5mC), H3K9me (K9me), and HP1 binding influence methylation of H3K27 by PRC2. Conversely, histone modifications associated with transcription such as H3K4me (K4me), H3K36me (K36me), and H3K27ac (K27ac), as well as RNA can directly inhibit PRC2 catalytic activity to prevent H3K27me at regions of active gene expression. Genomic regions that do not contain features of active or repressed chromatin may be targeted by PRC2. Other properties of the chromatin environment such as nucleosome occupancy, chromosome conformation and location within the nucleus (not pictured) may also contribute to PRC2 target selection.
See this image and copyright information in PMC

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