The chromatin remodeler DDM1 prevents transposon mobility through deposition of histone variant H2A.W

Osakabe et al. report that the chromatin remodeler DDM1 silences transposable elements by mediating H2A.W deposition in Arabidopsis. Mobile transposable elements (TEs) not only participate in genome evolution but also threaten genome integrity. In healthy cells, TEs that encode all of the components that are necessary for their mobility are specifically silenced, yet the precise mechanism remains unknown. Here, we characterize the mechanism used by a conserved class of chromatin remodelers that prevent TE mobility. In the Arabidopsis chromatin remodeler DECREASE IN DNA METHYLATION 1 (DDM1), we identify two conserved binding domains for the histone variant H2A.W, which marks plant heterochromatin. DDM1 is necessary and sufficient for the deposition of H2A.W onto potentially mobile TEs, yet does not act on TE fragments or host protein-coding genes. DDM1-mediated H2A.W deposition changes the properties of chromatin, resulting in the silencing of TEs and, therefore, prevents their mobility. This distinct mechanism provides insights into the interplay between TEs and their host in the contexts of evolution and disease, and potentiates innovative strategies for targeted gene silencing.

Automated summary

The study by Osakabe et al. demonstrates that the chromatin remodeler DDM1 plays a crucial role in silencing transposable elements by mediating H2A.W deposition in Arabidopsis, preventing their mobility. This discovery sheds light on the essential mechanism of chromatin remodelers in regulating TEs and provides new insights into the interaction between TEs and their host in the contexts of evolution and disease.