DNA Labeling Using DNA Methyltransferases.

DNA methyltransferases (MTases) uniquely combine the ability to recognize and covalently modify specific target sequences in DNA using the ubiquitous cofactor S-Adenosyl-L-methionine (AdoMet). Although DNA methylation plays important roles in biological signaling, the transferred methyl group is a poor reporter and is highly inert to further biocompatible derivatization. To unlock the biotechnological power of these enzymes, extended cofactor AdoMet analogs have been developed that enable targeted MTase-directed attachment of larger moieties containing functional or reporter groups onto DNA. As the enlarged cofactors are not always compatible with the active sites of native MTases, steric engineering of the active site has been employed to optimize their alkyltransferase activity. In addition to the described cofactor analogs, recently discovered atypical reactions of DNA cytosine-5 MTases involving non-cofactor-like compounds can also be exploited for targeted derivatization and labeling of DNA. Altogether, these approaches offer new powerful tools for sequence-specific covalent DNA labeling, leading to a variety of useful techniques in DNA research, diagnostics and nanotechnologies, and have already proven practical utility for optical DNA mapping and high-throughput epigenome studies.