What is Bisulfite Conversion?
In mammalian DNA, the main modified base is 5-methylcytosine (5-mC), which occurs in 2-5 % of all cytosine residues (typically those that are located in CpG doublets) (1). Bisulfite conversion is a reaction between the bisulfite molecule and unmodified cytosines in single-stranded DNA (2–3). The reaction converts cytosine to uracil, whereas 5-mC is unreactive. The modified DNA can then be amplified via PCR to understand its methylation status (Figure 1). Figure 1. Distinguish methylated DNA via bisulfite modification and sequencing analysis. Methylated Cs (left-hand set of arrows) are protected during bisulfite conversion (Step 1) and transcribed as Gs during PCR (Step 2). Nonmethylated Cs (right-hand set of arrows) are converted to Uracils during bisulfite conversion (Step 1) and transcribed as As during PCR (Step 2). Methylated domains are identified by comparing sequencing data for converted and unconverted DNA.
