One-Electron Photooxidation and Site-Selective Strand Cleavage at 5-Methylcytosine in DNA by Sensitization with 2-Methyl-1,4-naphthoquinone-Tethered Oligonucleotides

详细信息    查看全文

• 作者：Kazuhito Tanabe ; Hisatsugu Yamada ; Sei-ichi Nishimoto
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：June 27, 2007
• 年：2007
• 卷：129
• 期：25
• 页码：8034 - 8040
• 全文大小：246K
• 年卷期：v.129,no.25(June 27, 2007)
• ISSN：1520-5126

文摘

Photosensitized one-electron oxidation was applied to discriminate a specific base site of5-methylcytosine (^mC) generated in DNA possessing a partial sequence of naturally occurring p53 gene,using a sensitizing 2-methyl-1,4-naphthoquinone (NQ) chromophore tethered to an interior of oligodeoxynucleotide (ODN) strands. Photoirradiation and subsequent hot piperidine treatment of the duplex consistingof ^mC-containing DNA and NQ-tethered complementary ODN led to oxidative strand cleavage selectivelyat the ^mC site, when the NQ chromophore was arranged so as to be in close contact with the target ^mC.The target ^mC is most likely to be one-electron oxidized into the radical cation intermediate by the sensitizationof NQ. The resulting ^mC radical cation may undergo rapid deprotonation and subsequent addition ofmolecular oxygen, thereby leading to its degradation followed by strand cleavage at the target ^mC site. Incontrast to ^mC-containing ODN, ODN analogs with replacement of normal cytosine, thymine, adenine, orguanine at the ^mC site underwent less amount of such an oxidative strand cleavage at the target base site,presumably due to occurrence of charge transfer and charge recombination processes between the baseradical cation and the NQ radical anion. Furthermore, well designed incorporation of the NQ chromophoreinto an interior of ODN could suppress a competitive strand cleavage at consecutive guanines, whichoccurred as a result of positive charge transfer. Thus, photosensitization by an NQ-tethered ODN led toone-electron oxidative strand cleavage exclusively at the target ^mC site, providing a convenient method ofdiscriminating ^mC in naturally occurring DNA such as human p53 gene as a positive band on a sequencinggel.