Stability, Miscoding Potential, and Repair of 2'-Deoxyxanthosine in DNA: Implications for Nitric Oxide-Induced Mutagenesis
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- 作者：Gerald E. Wuenschell ; Timothy R. O'Connor ; and John Termini
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：April 1, 2003
- 年：2003
- 卷：42
- 期：12
- 页码：3608 - 3616
- 全文大小：149K
- 年卷期：v.42,no.12(April 1, 2003)
- ISSN：1520-4995
文摘
Nitric oxide (NO
) reacts with guanine in DNA and RNA to produce xanthine (X) as a majorproduct. Despite its potential importance in NO-mediated mutagenesis, the biochemical properties of Xin polynucleotides have been relatively unexplored. We describe the synthesis and chemical characterizationof xanthine-containing oligonucleotides and report on the susceptibility of X to depurination, its miscodingpotential during replication by polymerases, and its recognition and excision by several members of thebase excision repair (BER) family of DNA glycosylases. At neutral pH, X was found to be only slightlyless stable than guanine to depurination (kX/kG = 1.19), whereas at pH 
4 the depurination rate exceededthat of G by more than an order of magnitude. HIV-1 RT inserted dCTP and dTTP with approximatelyequal frequencies opposite X in a DNA template, whereas DNA Pol 1(KF-) preferentially inserted dCTP.Several DNA glycosylases were found to excise X specifically in X·C base pairs, whereas activity towardX·G, X·A, or X·T pairs was detected only for AlkA. The order of reactivity of glycosylases for theremoval of X·C base pairs was found to be AlkA > Mpg > Nth > Fpg. Implications of these results forthe induction of mutations by nitric oxide are discussed.
) reacts with guanine in DNA and RNA to produce xanthine (X) as a majorproduct. Despite its potential importance in NO-mediated mutagenesis, the biochemical properties of Xin polynucleotides have been relatively unexplored. We describe the synthesis and chemical characterizationof xanthine-containing oligonucleotides and report on the susceptibility of X to depurination, its miscodingpotential during replication by polymerases, and its recognition and excision by several members of thebase excision repair (BER) family of DNA glycosylases. At neutral pH, X was found to be only slightlyless stable than guanine to depurination (kX/kG = 1.19), whereas at pH 4 the depurination rate exceededthat of G by more than an order of magnitude. HIV-1 RT inserted dCTP and dTTP with approximatelyequal frequencies opposite X in a DNA template, whereas DNA Pol 1(KF-) preferentially inserted dCTP.Several DNA glycosylases were found to excise X specifically in X·C base pairs, whereas activity towardX·G, X·A, or X·T pairs was detected only for AlkA. The order of reactivity of glycosylases for theremoval of X·C base pairs was found to be AlkA > Mpg > Nth > Fpg. Implications of these results forthe induction of mutations by nitric oxide are discussed.