Electrochemical assay for continuous monitoring of dynamic DNA methylation process.

A simple electrochemical strategy is reported for continuous monitoring of dynamic DNA methylation process over time. An electrochemical sensor was prepared by co-assembling of DNA probe and 6-mercapto-1-hexanol onto a gold electrode. The top of the DNA probe was labeled with 6-ferrocenylhexanethiol modified gold nanoparticle. The charge density between the C•G base pair was verified to be slightly reduced by DNA methylation, and could be further decelerated by ~ 25% upon co-locating a Br group onto methylated cytosine (mC). Therefore, in the presence of NaIO4/LiBr, the progressively methylated DNA on the sensor showed a clearly decreasing current over methylation time. The dynamic DNA methylation process was indicated continuously from the current decrease ratio, with a limit of detection of 0.0372µM. The strategy is convenient, cost-effective, and enable continuous profiling methylation process without distortion. Besides, the strategy was successfully applied for the studies on inhibitor screening and flanking sequence preference of DNA methyltransferase 3a. The results show that the activity of DNA methyltransferase 3a can be mildly inhibited by epigallocatechin gallate, and varies towards different flanking sequence with an order of 5′-CCGG-3′ < 5′-CGCG-3′ < 5′-CGCA-3′.