Electrochemical strategy for sensing DNA methylation and DNA methyltransferase activity

The present work demonstrates a novel signal-off electrochemical method for the determination of DNA methylation and the assay of methyltransferase activity using the electroactive complex [Ru(NH3)6]3+ (RuHex) as a signal transducer. The assay exploits the electrostatic interactions between RuHex and DNA strands. Thiolated single strand DNA1 was firstly self-assembled on a gold electrode via Au–S bonding, followed by hybridization with single strand DNA2 to form double strand DNA containing specific recognition sequence of DNA adenine methylation MTase and methylation-responsive restriction endonuclease Dpn I. The double strand DNA may adsorb lots of electrochemical species ([Ru(NH3)6]3+) via the electrostatic interaction, thus resulting in a high electrochemical signal. In the presence of DNA adenine methylation methyltransferase and S-adenosyl-l-methionine, the formed double strand DNA was methylated by DNA adenine methylation methyltransferase, then the double strand DNA can be cleaved by methylation-responsive restriction endonuclease Dpn I, leading to the dissociation of a large amount of signaling probes from the electrode. As a result, the adsorption amount of RuHex reduced, resulting in a decrease in electrochemical signal. Thus, a sensitive electrochemical method for detection of DNA methylation is proposed. The proposed method yielded a linear response to concentration of Dam MTase ranging from 0.25 to 10 U mL−1 with a detection limit of 0.18 U mL−1 (S/N = 3), which might promise this method as a good candidate for monitoring DNA methylation in the future.

A novel and highly sensitive signal-off electrochemical method to monitor DNA methylation and DNA adenine methylation methyltransferase activity is proposed.Figure optionsDownload as PowerPoint slideHighlights
► An electrochemical strategy for sensing DNA methylation and DNA methyltransferase activity was proposed.
► A methylation-responsive DNA biosensor was fabricated.
► This assay was based on electrostatic adsorption of [Ru(NH3)6]3+ on the anionic DNA biosensor.
► A low detection limit (0.18 U mL−1) was obtained without any amplification.
► This strategy can be applied to qualification of activity of other methyltransferases.