Novel genomic island modifies DNA with 7-deazaguanine derivatives

The discovery of a novel modification system that inserts 7-deazaguanine derivatives in DNA, modifications thought until now to occur only in RNA, is an excellent illustration of the power of biological evolution to alter the ultimate function not only of the distinct proteins but also of entire metabolic pathways. The extensive lateral transfer of the gene cluster responsible for this modification highlights its significance as a previously unrecognized foreign DNA defense system that bacteria and phages use to protect their genomes. The characterization of these DNA modification pathways also opens the door to novel tools to manipulate nucleic acids.