Sequence-selective recognition and cleavage of double-helical DNA

Single sites within long double-helical DNA molecules can be recognized by a variety of mechanisms. Different strategies have been used to adapt sequence-specific recognition to sequence-specific cleavage of duplex DNA. Any nucleic acid can be converted into an artificial nuclease by the attachment of a cleaving reagent. Alternatively, a sequence-specific ligand can be used to protect a methylase recognition site from methylation. The protected site may then be cleaved selectively by a restriction endonuclease (the so-called 'Achilles heel' cleavage technique). Recent developments in this area have shown that it is possible to cleave chromosomal DNA at single sites within bacterial and eukaryotic genomes.