Dual control of ROS1-mediated active DNA demethylation by DNA damage-binding protein 2 (DDB2).

By controlling gene expression, DNA methylation contributes to key regulatory processes during plant development. Genomic methylation patterns are dynamic and must be properly maintained and/or re-established upon DNA replication and active removal, and therefore require sophisticated control mechanisms. Here we identify direct interplay between the DNA repair factor DNA damage-binding protein 2 (DDB2) and the active DNA demethylation pathway in Arabidopsis thaliana. We show that DDB2 forms a complex with and AGO4 and that they act at the duanyu16701 locus to modulate levels of DNA methylation and therefore duanyu16701 expression. We found that DDB2 represses enzymatic activity of DNA demethylation intermediates generated by duanyu16701 are processed by the DNA 3'-phosphatase ZDP and the apurinic/apyrimidinic endonuclease APE1L, and we also show that DDB2 interacts with both enzymes and stimulates their activities. Taken together, our results indicate that DDB2 acts as a critical regulator of duanyu16701-mediated active DNA demethylation.

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