Detection of single methylated cytosine using junction-forming DNA probes

Abstract

DNA methylation is an epigenetic mechanism for transcriptional regulation. The methylation process controls cellular differentiation and is defective in many diseases including cancer. Therefore, the development of a simple method for analysing cytosine methylation in a target gene is required. Here we report a conceptually new method for sequence-selective chemical modification of a single cytosine in single-stranded DNA (ssDNA) using two DNA probes to form a DNA three-way junction with the ssDNA. The method was successfully used in a simple quantitative polymerase-chain-reaction-based assay for discrimination of a single methylated cytosine.