BioMed Research International / 2017 / Article / Fig 1

Review Article

New Insights into the Epigenetics of Hepatocellular Carcinoma

Figure 1

CpG methylation. (a) DNA methylation is catalyzed by three methyl transferase genes (DNMT1, DNMT3a, and DNMT3b) that add methyl group (CH3) at 5th carbon position of pyrimidine ring of cytosine. S-adenosyl methionine (SAM-CH3) acts as a methyl donor. (b) Cytosine to cytosine sulfonate: sulfonation of cytosine causes C to T transition followed by deamination. Cytosine sulfonate to uracil sulfonate: conversion of cytosine sulfonate to uracil sulfonate leads to alkali desulfonation. Uracil sulfonate is converted into uracil. PCR distinguishes methylated CpG from unmethylated CpG because methylated cytosine resists this chemical treatment [124, 125].