Detection and Quantification of Methylation in Genomic DNA

摘要

Methylation is a major modification of genomic DNA in both eukaryotes and prokaryotes. It protects DNA from restriction enzymes in prokaryotes and serves as the molecular locker for cellular development. Lower eukaryotes, plant and bacterial DNA contain three methylated nucleosides, namely, 5-methyl-2'-deoxycytidine (5mdC), N~(6)-methyl-2'-deoxyadenosine (N~(6)mdA) and N~(4)-methyl-2'-deoxycytidine (N~(4)mdC); however, only 5mdC was detected in mammals till now. Earlier studies by restriction enzymes sensitive to adenine methylation suggested the existence of N~(6)mdA in Arabidopsis thaliana (Ashapkin, V. V. et al. FEBS Lett. 2002), mouse and rat DNA (Kay P.H. et al. Gene 1994 & Reyes E.M. et al J. Androl. 1997). Here, we employ LC-MS/MS to detect and quantify global methylation in genomic DNA of different organisms.