Skip to main content
. Author manuscript; available in PMC: 2017 Dec 5.
Published in final edited form as: Adv Exp Med Biol. 2017;963:337–358. doi: 10.1007/978-3-319-50044-7_20

Figure 5. DNA methylation/demethylation enzymes.

Figure 5

Methylation of the promoter regions of genes significantly suppresses transcription by direct inhibition of transcription factor binding and recruitment of methyl-CpG-binding proteins within their recognition sites of transcription factors. DNA methylation occurs at carbon 5 of cytosine (5-methylcytosine [5mC]) in cytosine-phosphate-guanine dinucleotides (CpG) dinucleotides. DNA (cytosine-5-)-methyltransferase 1 (DNMT1) maintains DNA methylation patterns during cell proliferation via methylation of a hemi-methylated nascent DNA strand. DNMT3A and DNMT3B are required for genome-wide de novo methylation and play crucial roles in the establishment of DNA methylation patterns. Methylation by DNMTs is counterbalanced by DNA demethylation. TET oxidizes 5mC to 5-hydroxymethylcytosine (5hmC) and subsequently to 5-formyl cytosine (5fC) and 5-carboxy cytosine (5caC). The carboxyl group of 5caC is excised by thymine DNA glycolase (TDG) to restore cytosine. An active demethylation pathway through consecutive oxidation of 5-methylcytosine (5mC) mediated by TET (ten eleven translocation) proteins and subsequent base excision repair (BER) in mammalian systems DNA methylation dynamics. Reprinted and modified from Heo et al(Heo et al., 2016) with permission of the publisher.