Anin M F, Gaucheron F, Leng M
Centre de Biophysique Moléculaire, CNRS, Orléans, France.
Nucleic Acids Res. 1992 Sep 25;20(18):4825-30. doi: 10.1093/nar/20.18.4825.
Recently, we have shown that the adduct formed in the reaction between the platinum-triamine complex cis-[Pt(NH3)2(N7-N-methyl-2-diazapyrenium)Cl]2+ and one single-stranded oligonucleotide was stable but became labile as soon as the platinated oligonucleotide was paired with its complementary strand (Gaucheron et al. Proc. Natl. Acad. Sci. USA 88, 3516-3519 (1991)). To generalize this finding we have now studied large DNA fragments containing several adducts. The stability of the adducts within single-stranded DNA is demonstrated by absorption spectrophotometry and by replication mapping experiments. Several approaches are used to prove the lability of the adducts within double-stranded DNA. Replication mapping experiments reveal that an unmodified single-stranded DNA when mixed with double-stranded DNA modified by the platinum-triamine complex behaves as a single-stranded DNA modified by the triamine complex. After double-stranded DNA is modified by the platinum-triamine complex, intrastrand and interstrand cross-links are progressively formed during subsequent incubation as revealed by transcription mapping experiments and gel electrophoresis under denaturing conditions. Finally, replication mapping experiments show that the lability of the adducts within a double-stranded DNA depends upon the nature of the flanking nucleotide residues. All these results support the proposal that the DNA double helix acts as a catalyst in the reaction between DNA, cis-diamminedichloroplatinum(II) and N-methyl-2,7-diazapyrenium.
最近，我们已经表明，铂-三胺配合物顺式-[Pt(NH₃)₂(N₇-N-甲基-2-二氮杂芘)Cl]²⁺与一条单链寡核苷酸反应形成的加合物是稳定的，但一旦铂化寡核苷酸与其互补链配对，该加合物就会变得不稳定（高谢龙等人，《美国国家科学院院刊》88，3516 - 3519(1991)）。为了推广这一发现我们现在研究了含有多个加合物的大DNA片段。通过吸收分光光度法和复制图谱实验证明了单链DNA中加合物的稳定性。我们采用了几种方法来证明双链DNA中加合物的不稳定性。复制图谱实验表明，当未修饰的单链DNA与经铂-三胺配合物修饰的双链DNA混合时，其表现如同经三胺配合物修饰的单链DNA。经铂-三胺配合物修饰后的双链DNA，如转录图谱实验和变性条件下的凝胶电泳所示，在随后的温育过程中会逐渐形成链内和链间交联。最后，复制图谱实验表明，双链DNA中加合物的不稳定性取决于侧翼核苷酸残基的性质。所有这些结果都支持了这样一种观点，即DNA双螺旋在DNA、顺-二氯二氨铂(II)和N-甲基-2,7-二氮杂芘之间的反应中起催化剂的作用。
