Role of Polycomb in the control of transposable elements

It is generally considered that Polycomb Repressive Complex (PRC)2 deposits the histone mark H3K27me3 on silent protein-coding genes, while transposable elements are repressed by DNA and/or H3K9 methylation. Yet, there is increasing evidence that PRC2 also targets and even silences transposable elements in representatives of several distantly related eukaryotic lineages. In plants and animals, H3K27me3 is present on transposable elements in mutants and specific cell types devoid of DNA methylation. In this Opinion, we summarize the experimental evidence for this phenomenon across the eukaryotic kingdom, and discuss its functional and evolutionary significance. We hypothesize that an ancestral role of Polycomb group (PcG) proteins was to silence transposable elements.

Automated summary

This article summarizes the experimental evidence of Polycomb Repressive Complex 2 (PRC2) targeting and silencing transposable elements across the eukaryotic kingdom, in addition to depositing on silent protein-coding genes, discussing its functional and evolutionary significance. The authors hypothesize that an ancestral role of Polycomb group (PcG) proteins was to silence transposable elements.