DNA methylation is one of the best types of epigenetic methods as it allows genes that are turned off to stay off completely. It is a repressive mark that occurs in CpG islands (long stretches of DNA containing Cytosine and Guanine as dinucleotides in a repeating order in the 5′ to 3′ direction i.e CGCGCGC…).
Mechanism of DNA methylation
Two important processes include:
- DNA methylation happens on the fifth carbon of cytosine to form 5-methylcytosine (5mc) by DNA methyltransferases (DNMT's).
- DNMT's can be DNMT1 or DNMT3a and 3b. The former is used to methylate the unmethylated strand of DNA