DNA methyltransferases

HHMI News: Biotechnology's Newest Chemical Tool: "The enzymes at the heart of the study, known as DNA methyltransferases, are one of the tools cells use to turn genes on and off. By adding a simple cluster of four atoms - a carbon atom attached to three hydrogens, known to chemists as a methyl group - to specific bases within a DNA sequence, methyltransferases can effectively shut a gene off. Methylation plays an important role in embryonic development, genomic imprinting, and carcinogenesis because it regulates gene expression."