COPPER-DEPENDENT CLEAVAGE OF DNA BY BLEOMYCIN
COPPER-DEPENDENT CLEAVAGE OF DNA BY BLEOMYCIN
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DOI：
10.1021/bi00377a038
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发表时间：
1987-02-10
期刊：
影响因子：
2.9
通讯作者：
HECHT, SM
中科院分区：
文献类型：
--
作者：
EHRENFELD, GM;SHIPLEY, JB;HECHT, SM
进一步表征了在Cu和Fe存在下博来霉素的DNA链断裂。发现在Cu（II）或Cu（II）+二硫苏糖醇+博来霉素的混合物中容易发生DNA降解，但仅在添加顺序阻止Cu（II）-博来霉素的初始形成或允许足够的时间将所形成的Cu（II）-博来霉素还原成Cu（I）-博来霉素的情况下。在与铜离子螯合作用一致的实验条件下，铜离子选择剂浴铜灵可抑制Cu +二硫苏糖醇+博莱霉素介导的DNA链断裂。值得注意的是，发现在Fe和Cu存在下用博来霉素获得的DNA降解程度大于单独用任一金属离子获得的DNA降解程度。博来霉素的序列选择性的比较中存在的Cu和Fe使用32 P-末端标记的DNA双链体作为底物显示显着差异的网站sof DNA切割和切割的程度在网站共享的共同。对于去糖博莱霉素和decarbamoylbleomycin，其金属连接被认为是不同于博莱霉素itelf，它被发现，在Cu的存在下的DNA裂解的相对程度是不相同的顺序，在Fe的存在下获得的。博来霉素介导的氧合产物衍生自顺式-芪被发现在添加的Cu与添加的Fe的存在下在类型和量上不同。有趣的是，当过量的Fe加入到含有1：1的Fe（III）和博来霉素的反应混合物中时，虽然顺式-芪的产物形成减少，但与1：1的Cu和博来霉素相比，在含有5：1的反应中产物形成的程度提高了几乎4倍。这些实验的结果与Sugiura [Sugiura，y.（1979）Biochem. Biophys. Res. Commun. 90，375-383]，他首先证明了在O2和Cu（I）-博来霉素混合时活性氧物质的产生。
DNA strand scission by bleomycin in the presence of Cu and Fe was further characterized. It was found that DNA degradation occurred readily upon admixure of Cu9I) or Cu(II) + dithiothreitol + bleomycin, but only where the order of addition precluded initial formation of Cu(II)-bleomycin or where sufficient time was permitted for reduction of the formed Cu(II)-bleomycin to Cu(I)-bleomycin. DNA strand scission mediated by Cu + dithiothreitol + bleomycin was inhibited by the copper-selective agent bathocuprione when the experment was carried out under conditions consistent with Cu chelation by bathocuprione on the time scale of the experiment. Remarkably, it was found that the extent of DNA degrdation obtained with bleomycin in the presence of Fe and Cuwas greater than that obtained with either metal ion alone. A comparison of the sequence selectivity of bleomycin in the presence of Cu and Fe using 32P-end-labeled DNA duplexes as substrates revealed significant differences in site sof DNA cleavage and in the extent of cleavage at sites shared in common. For deglycobleomycin and decarbamoylbleomycin, whose metal ligation is believed to differ from that of bleomycin itelf, it was found that the relative extents of DNA cleavage in the presence of Cu were not in the same order as those obtained in the presence of Fe. The bleomycin-mediated oxygenation products derived from cis-stilbene were found to differ in type and amount in the presence of added Cu vs. added Fe. Interestingly, while product formation from cis-stilbene was decreased when excess Fe was added to a reaction mixture containing 1:1 Fe(III) and bleomycin, the extent of product formation was enhanced almost 4-fold in reactions that contained 5:1, as compared to 1:1, Cu and bleomycin. The results of these experiments are entirely consistent with the work of Sugiura [Sugiura, y. (1979) Biochem. Biophys. Res. Commun. 90, 375-383], who first demonstrated the generation of reactive oxygen species upon admixture of O2 and Cu(I)-bleomycin.