A novel combined bisulfite UDG assay for selective 5-methylcytosine detection.

DNA modification, a significant epigenetic event, largely affects genes' binding with the transcription factors and some other DNA binding proteins. Among DNA modifications, methylation, especially cytosine methylation is of great importance and attracts extensive studies as it leads to the silence of tumor-suppressor gene expression. In this work, a novel combined bisulfite Uracil-DNA glycosylase (UDG) assay has been developed on the basis of bisulfite modification to generate uracil from cytosine, subsequent UDG-mediated uracil elimination and ultimate DNA cleavage in alkaline condition. This strategy can be used to selectively detect exact number and loci of 5-methylcytosine residues regardless of sequence context. Moreover, it provides linear quantitative results of DNA methylation level across a wide range.