Detection of DNA methyltransferase activity using template-free DNA polymerization amplification based on aggregation-induced emission.

A sensitive and selective fluorescence assay for DNA methyltransferase (MTase) activity detection was designed based on aggregation-induced emission (AIE) and target initiated template-free DNA polymerization. Quaternized tetraphenylethene salt was synthesized as the AIE probe, which binds to single-stranded DNA by electrostatic interaction. A hairpin probe was designed with a specific sequence for DNA MTase. In the presence of DNA MTase, the methylation reaction initiated DNA polymerization with terminal deoxynucleotidyl transferase (TdT), which activated the fluorescence intensity through AIE. The designed DNA sensor displayed a linear response to concentrations of DNA adenine methyltransferase (Dam) MTase from 0.5 U·mL-1 to 100 U mL-1, with a limit of detection of 0.16 U mL-1. The assay was also effective for detection of DNA MTase activity in human serum and for showing the inhibitory effect of 5-fluorouracil on Dam MTase.