Pérez C, Leng M, Malinge J M
Centre de Biophysique Moléculaire, CNRS, Orléans, France.
Nucleic Acids Res. 1997 Feb 15;25(4):896-903. doi: 10.1093/nar/25.4.896.
In the reaction of the anticancer drug cis-diamminedichloroplatinum(II) (cis-DDP) with DNA, bifunctional intrastrand and interstrand cross-links are formed. In this work, we show that at 37 degrees C interstrand cross-links (ICL) are labile and rearrange into intrastrand cross-links. The ICL instability was first studied with a 10 base pairs (bp) double-stranded oligonucleotide containing a unique site-specific ICL resulting from chelation of the N7 position of two guanine residues on the opposite strands of DNA at the d(GC/GC) site by a cis-diammineplatinum(II) residue. The bonds between the platinum and the N7 of guanine residues within the interstrand adduct are cleaved. In 50 mM NaCl or NaClO4, this cleavage results in the formation of monofunctional adducts which subsequently form intrastrand cross-links. One cleavage reaction takes place per cross-linked duplex in either of both DNA strands. Whereas the starting cross-linked 10 bp duplex is hydrogen bonded, the two complementary DNA strands separate after the cleavage of the ICL. Under these conditions, the cleavage reaction is irreversible allowing its rate measurement (t1/2= 29+/-2 h) and closure of monofunctional adducts to intrastrand cross-links occurs within single-stranded DNA. Within a longer cross-linked oligonucleotide (20 bp), ICL are apparently more stable (t1/2= 120+/-12 h) as a consequense of monofunctional adducts closure back to ICL. We propose that the ICL cleavage is reversible in DNA and that these adducts rearrange finally into intrastrand cross-links. Our results could explain an 'ICL unhooking' in previously reported in vivo repair studies [Zhenet al. (1993)Carcinogenesis14, 919-924].
在抗癌药物顺二氨二氯铂（II）（顺铂）与DNA的反应中，会形成双功能的链内和链间交联。在这项工作中，我们表明在37摄氏度时，链间交联（ICL）不稳定，并重新排列成链内交联。首先用一个10个碱基对（bp）的双链寡核苷酸研究了ICL的不稳定性，该寡核苷酸含有一个独特的位点特异性ICL，它是由顺二氨铂（II）残基在d（GC/GC）位点螯合DNA两条互补链上两个鸟嘌呤残基的N7位置而产生的。铂与链间加合物中鸟嘌呤残基的N7之间的键被切断。在50 mM NaCl或NaClO4中，这种切割导致形成单功能加合物，随后形成链内交联。每条交联的双链DNA的两条链中各发生一次切割反应。起始的交联10 bp双链是通过氢键结合的，ICL切割后两条互补DNA链分离。在这些条件下，切割反应是不可逆的，从而可以测量其速率（t1/2 = 29±2小时），并且单功能加合物在单链DNA内封闭形成链内交联。在较长的交联寡核苷酸（20 bp）中，由于单功能加合物重新封闭形成ICL，ICL显然更稳定（t1/2 = 120±12小时）。我们提出ICL切割在DNA中是可逆的，并且这些加合物最终重新排列成链内交联。我们的结果可以解释先前报道的体内修复研究中出现的“ICL解钩”现象[Zhen等人（1993年）《癌变》14卷，919 - 924页]。
