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. Author manuscript; available in PMC: 2011 Apr 12.
Published in final edited form as: Nat Rev Genet. 2010 Mar;11(3):204–220. doi: 10.1038/nrg2719

Figure 6. Maintenance of DNA methylation in plants and mammals.

Figure 6

(A) Model depicting maintenance of CG methylation during replication. Dnmt1 is proposed to be recruited to replication foci through interactions with UHRF1, an SRA domain protein that specifically interacts with hemi-methylated DNA, and with PCNA. Once recruited, Dnmt1 functions to maintain methylation patterns by restoring the hemi-methylated DNA to a fully methylated state. In plants, MET1, and the VIM family of SRA domain proteins, homologs of Dnmt1 and UHRF1, respectively, likely function in a similar manner to maintain CG methylation patterns. Black and Gray circles represent methylated and unmethylated cytosines respectively. (B) Model depicting maintenance of CHG methylation in plants. A reinforcing loop of DNA and histone methylation is proposed to maintain CHG methylation in plants. The CMT3 DNA methyltransferase maintains methylation in the CHG context, which is recognized by the SRA domain of the KYP/SUVH4 histone methyltransferase. KYP catalyzes H3K9 dimethylation (H3K9me2), a modification that is required for the maintenance of CHG methylation, and the chromodomain of CMT3 binds methylated histone 3 (H3) tails.