MBD5 and MBD6 couple DNA methylation to gene silencing through the J-domain protein SILENZIO. MBD5 and MBD6 couple DNA methylation to gene silencing through the J-domain protein SILENZIO

DNA methylation is associated with transcriptional repression of eukaryotic genes and transposons, but the downstream mechanism of gene silencing is largely unknown. Here we describe two Arabidopsis methyl-CpG binding domain proteins, MBD5 and MBD6, that are recruited to chromatin by recognition of CG methylation, and redundantly repress a subset of genes and transposons without affecting DNA methylation levels. These methyl-readers recruit a J-domain protein, SILENZIO, that acts as a transcriptional repressor in loss-of-function and gain-of-function experiments. J-domain proteins often serve as co-chaperones with HSP70s. Indeed, we found that SILENZIO?s conserved J-domain motif was required for its interaction with HSP70s and for its silencing function. These results uncover an unprecedented role of a molecular chaperone J-domain protein in gene silencing downstream of DNA methylation. Overall design: This study includes 11 DAP-seq samples, 19 ChIP-seq samples, 5 BS-seq samples, 18 BS-PCR samples, 82 RNA-seq samples, 2 GRO-seq samples and 1 EM-seq. Please note that the MBD5-MYC and MBD6-MYC ChIP-seq data (lib5) is of higher quality than the MBD5-FLAG and MBD6-FLAG ChIP-seq data. The lists of methylation hypervariable bins and genes have been deposited under the sample GSM5026060 (BSseq_lib1_Col0_rep1). See methods of the paper for details