Bisulfite conversion

DNA methylation was the first discovered epigenetic mark and is the most widely studied topic in Epigenetics today. Many techniques have been developed to analyze DNA methylation, which can be divided into three groups:

1. Chemical modification with bisulfite
2. Affinity-based isolation of methylated DNA
3. Treatment with methylation-sensitive restriction enzymes

Bisulfite modification of DNA is the most commonly used, "gold standard" method for DNA methylation studies. Since bisulfite treatment introduces specific changes in the DNA sequence depending on the methylation status of individual cytosine residues, single nucleotide resolution information can be obtained, the most prominent advantage of this method. Various analyses can be performed on the altered sequence to retrieve this information: bisulfite sequencing, methylation-specific PCR, high resolution melting curve analysis, microarray-based approaches, and next-generation sequencing.

How it works

Treatment of DNA with bisulfite converts cytosine residues to uracil, but leaves 5-methylcytosine residues unaffected (see Figure 1).