Helissey P, Giorgi-Renault S, Colson P, Houssier C, Bailly C
Laboratoire de Chimie Thérapeutique, Faculté des Sciences Pharmaceutiques et Biologiques, UMR CNRS-Université René Descartes no. 8638, 4, Avenue de l'Observatoire, 75270 Paris Cedex 06, France.
Bioconjug Chem. 2000 Mar-Apr;11(2):219-27. doi: 10.1021/bc990131t.
We report the synthesis, DNA-binding and cleaving properties, and cytotoxic activities of R-128, a hybrid molecule in which a bis-pyrrolecarboxamide-amidine element related to the antibiotic netropsin is covalently tethered to a phenazine-di-N-oxide chromophore. The affinity and mode of interaction of the conjugate with DNA were investigated by a combination of absorption spectroscopy, circular dichroism, and electric linear dichroism. This hybrid molecule binds to AT-rich sequences of DNA via a bimodal process involving minor groove binding of the netropsin moiety and intercalation of the phenazine moiety. The bidentate mode of binding was evidenced by linear dichroism using calf thymus DNA and poly(dA-dT).(dA-dT). In contrast, the drug fails to bind to poly(dG-dC).poly(dG-dC), because of the obstructive effect of the guanine 2-amino group exposed in the minor groove of this polynucleotide. DNase I footprinting studies indicated that the conjugate interacts preferentially with AT-rich sequences, but the cleavage of DNA in the presence of a reducing agent can occur at different sequences not restricted to the AT sites. The main cleavage sites were detected with a periodicity of about 10 base pairs corresponding to approximately one turn of the double helix. This suggests that the cleavage may be dictated by the structure of the double helix rather than the primary nucleotide sequence. The conjugate which is moderately toxic to cancer cells complements the tool box of reagents which can be utilized to produce DNA strand scission. The DNA cleaving properties of R-128 entreat further exploration into the use of phenazine-di-N-oxides as tools for investigating DNA structure.
我们报道了R-128的合成、DNA结合与切割特性以及细胞毒性活性。R-128是一种杂合分子，其中与抗生素纺锤菌素相关的双吡咯甲酰胺-脒元素与吩嗪二-N-氧化物发色团共价连接。通过吸收光谱、圆二色性和电场线性二色性相结合的方法研究了该共轭物与DNA的亲和力和相互作用模式。这种杂合分子通过一种双峰过程与富含AT的DNA序列结合，该过程涉及纺锤菌素部分的小沟结合和吩嗪部分的嵌入。使用小牛胸腺DNA和聚（dA-dT）·（dA-dT）通过线性二色性证明了双齿结合模式。相比之下，由于该多核苷酸小沟中暴露的鸟嘌呤2-氨基的阻碍作用，该药物无法与聚（dG-dC）·聚（dG-dC）结合。DNase I足迹研究表明，该共轭物优先与富含AT的序列相互作用，但在还原剂存在下DNA的切割可发生在不限于AT位点的不同序列处。主要切割位点的检测周期约为10个碱基对，对应于双螺旋大约一圈。这表明切割可能由双螺旋结构而非初级核苷酸序列决定。对癌细胞具有中等毒性的该共轭物补充了可用于产生DNA链断裂的试剂工具箱。R-128的DNA切割特性促使人们进一步探索将吩嗪二-N-氧化物用作研究DNA结构的工具。
