Nováková O, Vrána O, Kiseleva V I, Brabec V
Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno.
Eur J Biochem. 1995 Mar 15;228(3):616-24. doi: 10.1111/j.1432-1033.1995.tb20301.x.
Modifications of natural DNA and synthetic double-stranded oligodeoxyribonucleotides by cis-diamminedichloro-trans-dihydroxyplatinum(IV) (oxoplatin) were studied by means of ELISA, Maxam-Gilbert footprinting techniques, HPLC of enzymically digested DNA, and transcription assay. It was found that oxoplatin can bind DNA directly without addition of a reducing agent. In addition, the antibodies elicited against DNA modified by cisplatin were not competitively inhibited by DNA modified by oxoplatin. However, DNA containing the adducts of oxoplatin became a strong inhibitor of these antibodies, if it was subsequently treated with ascorbic acid, which is a reducing agent. These results were interpreted to mean that oxoplatin can form DNA adducts containing the platinum moiety in the quadrivalent state. The direct irreversible binding of the platinum(IV) drug is, however, slow as compared to the reaction of its platinum(II) counterpart. It was also found that oxoplatin preferentially binds to guanine residues and can form DNA intrastrand and interstrand cross-links containing platinum(IV). The DNA adducts containing platinum(IV) can inhibit in vitro transcription by a prokaryotic DNA-dependent RNA polymerase. We find that the platinum(IV) complex binds to DNA at similar sites as its platinum(II) counterpart. On the other hand, the DNA adducts containing the platinum(II) or platinum(IV) analogues differ in the number of ligands and the formal charge on their platinum center. We suggest that these differences could be responsible for distinct conformational features and stability of DNA modified by platinum(II) or platinum(IV) complexes.
采用酶联免疫吸附测定（ELISA）、马克萨姆-吉尔伯特足迹法、酶切DNA的高效液相色谱法（HPLC）以及转录分析等方法，研究了顺二氨二氯反二羟基铂（IV）（奥沙铂）对天然DNA和合成双链寡脱氧核糖核苷酸的修饰作用。研究发现，无需添加还原剂，奥沙铂就能直接与DNA结合。此外，针对顺铂修饰的DNA产生的抗体，不会被奥沙铂修饰的DNA竞争性抑制。然而，如果随后用还原剂抗坏血酸处理，含有奥沙铂加合物的DNA会成为这些抗体的强效抑制剂。这些结果被解释为意味着奥沙铂能够形成含有四价铂部分的DNA加合物。然而，与其二价铂对应物的反应相比，铂（IV）药物的直接不可逆结合较为缓慢。还发现奥沙铂优先与鸟嘌呤残基结合，并能形成含有铂（IV）的DNA链内和链间交联。含有铂（IV）的DNA加合物能够抑制原核DNA依赖性RNA聚合酶的体外转录。我们发现铂（IV）配合物与其二价铂对应物在相似的位点与DNA结合。另一方面，含有二价铂或铂（IV）类似物的DNA加合物在配体数量及其铂中心的形式电荷方面存在差异。我们认为这些差异可能导致二价铂或铂（IV）配合物修饰的DNA具有不同的构象特征和稳定性。
