Fig. 6

A revised model illustrating complementary DNMT3a/3b de novo activity and DNMT1 maintenance activity at three genomic regions. Via interacting with proteins such as UHRF1 at replication forks, DNMT1 plays a dominant role in maintaining methylation at retrotransposon LTRs (region 1), whereas DNMT3a/3b are mainly responsible for methylation at retrotransposon LINEs (region 2) or genomic regions with CHH sites (region 3). Loss of DNMT3a/3b or DNMT1 results in hypomethylated retrotransposon LTRs or LINEs