Determination of Methylation Site of DNA-Methyltransferase

Using a new method based on a combination of bisulfite reaction, the repair enzyme uracil-DNA glycosylase, and synthetic oligodeoxyribonucleotides, the methylation site of DNA-methyltransferase X (M· X) from Neisseria lactamica was established to be the inner cytosine in the double-stranded pentanucleotide recognition sequence 5′-CCNGG-3′ (where N = any nucleoside). 5-Methylcytosine (m C) type modification by M· X was confirmed by the use of oligonucleotide substrates that contain 5-fluoro-2′-deoxycytidine.