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. Author manuscript; available in PMC: 2014 Aug 1.
Published in final edited form as: Environ Mol Mutagen. 2013 Feb 26;54(7):533–541. doi: 10.1002/em.21762

Figure 1.

Figure 1

Promoter methylation and transcriptional regulation. (A) The gene is transcriptionally competent when the promoter region is unmethylated. (B) S-adenosylmethionine (SAM) donates a methyl group, which is covalently attached to the 5-carbon of a CpG (represented by the blue lollipops) in a reaction catalyzed by DNA methyltransferase (DNMT). Methylation of the promoter region can inhibit the binding of transcription factors and/or recruit repressors and is typically associated with transcriptional inactivation.