OBJECTIVETo establish a rapid and convenient method of DNA modification by bisulfite sodium for the detection of DNA methylation.

METHODSThrough increasing the bisulfite sodium concentration and the temperature of treatment, cutting down the modification time, besides using glassmilk to adsorb the DNA in the purification and recovery, to improve the methods of DNA modification. Efficiency of cytosine converted to thymine in MAGE-A3 gene and DAP-K gene fragments were analyzed by bisulfite sequencing PCR in order to evaluate the DNA modification effect among the improved method, traditional method and kit method.

RESULTSThe operating time of test was shortened to about 3 hours by the improved method; conversion rate of unmethylated cytosine to thymine was over 99%; compared with the traditional method and kit method, there was no significant difference (χ(2) = 0.0564, P > 0.05); the improved method was only for the unmethylated cytosine conversion modification, and there was no significant difference in process of methylated cytosine converted to thymine comparing with the traditional method (χ(2) = 0.0149, P > 0.05).

CONCLUSIONThe improved method has high efficiency of DNA modification and has no significant effect on excessive modification;meanwhile, it has many advantages such as time-saving and easy to operate etc.