Molecular basis of locus-specific H3K9 methylation catalyzed by SUVH6 in plants

Significance As a hallmark of heterochromatin in eukaryotes, dimethylated histone H3 Lys9 (H3K9me2) is mainly catalyzed by SUVH family methyltransferases in plants. However, how histone methyltransferases are recruited to specific loci remains largely unknown. The present study demonstrated that a previously uncharacterized N-terminal motif of SUVH6 can be recognized by RNA- and chromatin-binding protein ASI1 to confer H3K9 methylation at most SUVH6-bound loci, giving rise to transcriptional or posttranscriptional regulation depending on the position of target loci. More importantly, SUVH6-ASI1 module-mediated H3K9me2 deposition is evolutionarily conserved in different plant species, suggesting a general mechanism in the delicate regulation of the homeostasis of H3K9 methylation in plants.