A sensitive electrochemical method for DNA methyltransferase assay and inhibitor screening based on DNA methylation-sensitive cleavage

A sensitive electrochemical method for detection of DNA methylation and assay of DNA methyltransferase (Dam) was investigated based on methylation-sensitive restriction endonuclease, DNA-Au bio bar code and enzymatic signal amplification. After the DNA probe was hybridized with complementary DNA sequence, and the obtained double-strand DNA (dsDNA) was further methylated by Dam MTase, it could be successively digested by Dpn I at the methylated sites. As a result, the bio bar code and streptavidin-horseradish peroxidase (S-HRP) could not be conjugated on the electrode surface through the specific interaction between biotin and S-HRP, where biotin was labeled at the DNA-Au bio bar code. Thus, only a low electrochemical reduction signal was obtained. However, the hybridized probe could hybrid with DNA-Au bio bar code, and then S-HRP could be conjugated on the electrode surface in the absence of Dam MTase and Dpn I, so a larger reduction current of enzymatic product was obtained. The change of the reduction current of enzymatic product was used to detect DNA methylation and Dam MTase activity. The detection limit of Dam MTase was 0.02 unit/mL (S/N = 3). Moreover, the inhibitions of mitomycin C, paclitaxel, chlorogenic acid and epicatechin were also investigated. Therefore, this method provided a sensitive platform for monitoring DNA methylation and DNA MTase activity.