DNA methyltransferase activity detection using the personal glucose meter

DNA methyltransferase (MTase), which catalyses the DNA methylation process, plays an essential role in gene transcription and is a potential biomarker for many types of cancer. Leveraging on the ease of use and portability of the readily accessible personal glucose meter (PGM), a simple method for the highly selective and quantitative detection of M.SssI CpG methyltransferase (M.SssI MTase) activity is developed. DNA-Invertase conjugates were hybridised with complementary biotin-modified DNA strands and these DNA duplexes were captured onto streptavidin-coated magnetic beads. Thereafter, methylation by M.SssI MTase was carried out, followed by restriction digest by Hpa II. The 5´-CCGG-3´ sequence present in the DNA duplexes serves as the recognition site for both Hpa II and M.SssI MTase (5´-CG-3´). Hpa II specifically cleaves at unmethylated 5´-CCGG-3´ sequence, and the invertase that remains on the methylated DNA, catalyses the hydrolysis of sucrose to glucose and fructose. It was found that the amount of glucose, indicated by the read-out signal of the PGM, is proportional to the M.SssI MTase methylation activity in the range of 0.5 to 80 U/mL with a limit of detection of 0.37 U/mL. This proposed method also showed high selectivity for M.SssI MTase, due to the highly specific recognition sequence present in the DNA strands. Inhibition studies with 5´-azacytidine demonstrated the capability of inhibition screening.