Seminars

Arabidopsis mom1 mutation releases TGS (Transcriptional Gene Silencing) of hypermethylated genes residing in heterochromatin without major changes of their DNA methylation1. This suggests that TGS mediated by MOM1 acts downstream or independently of DNA methylation. Recent studies revealed that at some loci MOM1 acts downstream of the RNA-directed DNA methylation2,3. MOM1 protein contains conserved plant-specific motif, named CMM2 (Conserved MOM Motif 2), which is necessary for MOM1 TGS activity4. The molecular function of CMM2 is still unknown. Here we present structural and functional analyses of CMM2, which revealed that CMM2 needs to form multimers to perform its TGS function. In addition, we performed a forward genetic screen for mom1 suppressors. So far 12 suppressor mutants have been isolated and the genomes of some of them were re-sequenced to identify the causative mutations. Current status of the suppressors characterization will be presented.