Figure 2. Maintenance of CpG and non-CpG methylation. (A) A short region of genomic DNA containing several sites of CpG methylation and non-CpG methylation (red spheres). (B) During DNA replication the ‘maintenance methyltransferase’ DNMT1 reinstates CpG methylation on the newly synthesized DNA strand (green) guided by CpG methylation on the template DNA strand. (C) Following DNA replication the ‘de novo methyltransferases’ DNMT3A and DNMT3B, in complex with DNMT3L, re-establishes non-CpG methylation.