What is DNA methylation?

DNA methylation is the process of selectively adding methyl groups to cytosine to form 5-cytosine under the action of DNA methyltransferase (Dnmt). It was defined as the fifth base when it was first discovered. In fact, it is an important epigenetic marker and plays an important role in the biological processes of regulating gene expression, maintaining chromatin structure, genetic imprinting, X chromosome inactivation and embryo development. It is like the most magical "hat" of DNA, bringing endless surprises to the world.

DNA methylation is one of the earliest discovered ways of gene modification. Methylation in eukaryotes only occurs on cytosine, which is the CpG dinucleotide under the action of DNA methyltransferases (DNMTs) Cytosine at the 5'-end is converted to 5'-methylcytosine. DNA methylation usually suppresses gene expression, and demethylation induces gene re-activation and expression. This DNA modification method realizes the regulation of gene expression without changing the gene sequence. The methylation status of vertebrate DNA is closely related to the regulation of growth and development. For example, when tumors occur, the degree of unmethylation of CpG sequences other than the CpG island of the tumor suppressor gene increases, and the CpG in CpG islands is highly methylated. Causes a decrease in the expression of tumor suppressor genes.