Recent progress regarding the development of artificial site-selective DNA cutters by chemical approaches are reviewed herein, with a special focus on site-selective cutters for single-stranded DNA. We employ a Ce(IV)/EDTA complex to serve as the catalyst, because it efficiently and selectively cuts single-stranded DNA. Using two complementary oligonucleotide additives, a gap structure is formed at the target site in the single-stranded DNA substrate. Owing to the substrate specificity of Ce(IV)/ EDTA, the gap site is preferentially hydrolyzed, resulting in a site-selective DNA scission. The scission site is easily determined using the Watson-Crick base-pairing rule; thus, both the sequence and scission specificity can be tuned according to demand. The site-selective scission is greatly promoted by attaching a multiphosphonate to the termini of the oligonucleotide additives and placing this ligand at the gap site. The scission fragments can be connected with foreign DNA using ligase, and the recombinant DNA expresses the corresponding protein in E. coli.
INTRODUCTIONThe role of DNA in storing and carrying genetic information is essential for the function and development of all living organisms. If the information stored within DNA can be rewritten by scientists, numerous applications in a variety of fields will be possible. On this basis, chemists, biochemists and biologists have long attempted to rewrite the information encoded within DNA using various approaches. One direct and straightforward approach to precisely alter the information contained by DNA is the site-selective scission of DNA at a target site, 1-11 followed by the appropriate manipulation of the DNA at this local site.Currently, in molecular biology, DNA is manipulated by the 'cut-and-paste' method. In this approach, DNA is first cut at a predetermined site by naturally occurring restriction enzymes, and the resultant fragment is connected with another DNA fragment using ligases. Here, the target gene is inserted, deleted or altered. This strategy is satisfactorily effective so long as small DNAs such as plasmids (composed of several thousand base pairs) are targeted. Unfortunately, this technology is insufficient for manipulating large DNAs; however, our interests have been gradually focusing on the manipulation of genomic DNAs of higher organisms. The key problem is the low site specificity of naturally occurring restriction enzymes (most of them recognize 4 to 8-bp DNA sequences). Statistically, the scission site of a restriction enzyme with 6-bp