Abstract

In eukaryotic organisms, numerous transposons and other repetitive sequences are subjected to DNA methylation-mediated transcriptional silencing in order to maintain genome stability. On the other hand, some repetitive sequences including repetitive genes and genes with repeat elements need to be protected from epigenetic silencing in order to be expressed. The ROS1 subfamily of 5-methylcytosine DNA glycosylases/lyases functions to prevent transcriptional gene silencing in Arabidopsis by active DNA demethylation. Our recent forward genetic screens have identified several proteins such as the histone acetyltransferase IDM1 , the alpha-crystallin domain-containing proteins IDM2 and IDM3 , and the methyl-DNA-binding protein MBD7 , that are required for ROS1 to demethylate some genomic loci including repetitive genes and genes containing repeat elements and to protect them from transcriptional silencing. Our results suggest that these proteins form a protein complex that helps to recognize ROS1 target loci and create a permissible chromatin environment for ROS1 to demethylate the target DNA .