Roupioz Yoann, Lhomme Jean, Kotera Mitsuharu
Chimie Bioorganique, L.E.D.S.S., Associé au CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France.
J Am Chem Soc. 2002 Aug 7;124(31):9129-35. doi: 10.1021/ja025688p.
Deoxyribonolactone in DNA is an oxidized abasic site damage that is produced by a variety of physical and chemical agents such as gamma-irradiation and ene-diyne antibiotics. The extent and biological significance of the lesion are poorly documented due to the high lability of the damaged DNA. The chemistry of degradation of deoxyribonolactone-containing DNA was investigated using oligonucleotides of different length (5-, 11-, 23-, 34-mers) in which the lactone was photochemically generated, as already reported, from oligonucleotide precursors containing a photoactive nitroindole residue. The procedure was successfully extended to double-strand synthesis by irradiation of the preformed duplex in which one strand contained the nitroindole residue. The degradation kinetics were investigated as a function of pH, temperature, length, and ionic strength. The cleavage fragments resulting from beta- and delta-eliminations were isolated and identified by (1)H NMR. It was found that the lesion is extremely sensitive to pH and temperature while slightly dependent upon ionic strength, length, and sequence. The cleavage rates for the beta- and delta-elimination steps are of the same order of magnitude. The deoxyribonolactone site leads to greater instability of DNA than the "regular" deoxyribose abasic site.
DNA中的脱氧核糖内酯是一种氧化脱碱基位点损伤，由多种物理和化学因素如γ射线照射和烯二炔抗生素产生。由于受损DNA的高度不稳定性，该损伤的程度和生物学意义鲜有文献记载。使用不同长度（5聚体、11聚体、23聚体、34聚体）的寡核苷酸研究了含脱氧核糖内酯DNA的降解化学，如已报道的那样，内酯是由含有光活性硝基吲哚残基的寡核苷酸前体通过光化学产生的。该方法通过照射预形成的双链体成功扩展到双链合成，其中一条链含有硝基吲哚残基。研究了降解动力学与pH、温度、长度和离子强度的关系。通过1H NMR分离并鉴定了由β-消除和δ-消除产生的裂解片段。发现该损伤对pH和温度极其敏感，而对离子强度、长度和序列的依赖性较小。β-消除和δ-消除步骤的裂解速率处于相同的数量级。脱氧核糖内酯位点导致DNA比“常规”脱氧核糖脱碱基位点具有更大的不稳定性。
