DNA methylation either antagonizes or promotes Polycomb recruitment at transposable elements in Arabidopsis

Here, we initially set out to test whether DNA methylation and H3K27me3 compete during TE silencing establishment in Arabidopsis. Although we observe this competition at one newly inserted transgenic TE, we unexpectedly find that H3K27me3 deposition at another neo-inserted TE requires the de novo methyltransferase DRM2, revealing that DNA methylation can also promote Polycomb recruitment.

Genome-wide H3K27me3 profiling in drm2, met1, and rdd mutants shows that DNA methylation either antagonizes or promotes H3K27me3 in a locus-specific manner, and that DNA demethylation also shapes H3K27me3 levels in vegetative tissues. Targeted methylation experiments demonstrate that DNA methylation directly influences PcG recruitment, and analyses using a drm2 catalytic mutant further confirm that this effect depends on DNA methylation itself rather than on DNA the methylation machinery.