The chromatin remodeler DDM1 silences transposons through deposition of the histone variant H2A.W

Silencing of transposons by the chromatin remodeler DDM1 is mediated by the deposition of heterochromatic H2A variants.Transposon mobility and silencing participates in genome evolution but also threaten genome integrity. DECREASED DNA METHYLATION 1 (DDM1) belongs to a conserved family of chromatin remodelers that are required to silence transposons, yet the underlying molecular mechanism has remained unknown. Here we show that DDM1 binds the histone variant H2A.W through two conserved domains that are required to deposit H2A.W and maintain transposon silencing. The mechanism of transcriptional silencing described here is likely shared among chromatin remodelers of the DDM1 family and heterochromatic H2A variants that have evolved in mammals.