Exploiting biology’s own chemical toolbox, researchers have developed a new technique that will allow them to modify specific sequences within a DNA molecule. The approach will not only help reveal the impact of biochemical alterations to DNA, but could have far-reaching implications for DNA-based medical diagnosis and nanobiotechnology. Combining chemistry with biotechnology, Saulius Klimasauskas, a Howard Hughes Medical Institute (HHMI) international research scholar at the Institute of Biotechnology in Vilnius, Lithuania, and chemists at the Institute of Organic Chemistry in Aachen, Germany, have harnessed a group of essential enzymes to add various chemical groups to DNA, thereby altering its function. The work was published in an early online publication on November 27, 2005 in Nature Chemical Biology. 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.