Algueró Berta, Pedroso Enrique, Marchán Vicente, Grandas Anna
Departament de Química Orgànica, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
J Biol Inorg Chem. 2007 Aug;12(6):901-11. doi: 10.1007/s00775-007-0243-9. Epub 2007 May 30.
Platinated oligonucleotides are promising tools for the control of gene expression, since they may target and cross-link nucleic acid chains. Here we describe a method for the preparation of platinated oligonucleotides that has proved able to selectively cross-link complementary sequences, making use of 5-methylcytidine analogs with thioether or imidazole groups attached to the 4-position. These nucleoside analogs were derivatized as phosphoramidites and introduced in oligonucleotide chains using standard phosphite triester chemistry. Different oligonucleotide sequences containing either one or two analogs appending from the 5'-end were synthesized and used in preliminary platination studies. The reaction of transplatin with oligonucleotides containing the thioether-modified nucleobase was fast, but generally afforded unstable adducts and complex reaction mixtures. The imidazole-containing oligonucleotides reacted with transplatin much more slowly, in particular at slightly basic pH, and it was found that the imidazole-modified cytosine was less reactive than the natural nucleobases. In contrast, transplatin selectively reacted with the thioether and imidazole groups of oligonucleotides containing the two cytosine analogs in neighboring positions, even in the presence of the four nucleobases and particularly three guanines, affording platinated oligonucleotides suitable for cross-linking.
铂化寡核苷酸是控制基因表达的有前景的工具，因为它们可以靶向并交联核酸链。在此，我们描述了一种制备铂化寡核苷酸的方法，该方法已证明能够选择性地交联互补序列，利用了在4位连接有硫醚或咪唑基团的5-甲基胞苷类似物。这些核苷类似物被衍生化为亚磷酰胺，并使用标准亚磷酸三酯化学方法引入寡核苷酸链中。合成了从5'-端连接有一个或两个类似物的不同寡核苷酸序列，并用于初步的铂化研究。反式铂与含有硫醚修饰核碱基的寡核苷酸的反应很快，但通常产生不稳定的加合物和复杂的反应混合物。含咪唑的寡核苷酸与反式铂的反应要慢得多，特别是在略碱性的pH值下，并且发现咪唑修饰的胞嘧啶比天然核碱基的反应性更低。相反，反式铂即使在存在四个核碱基特别是三个鸟嘌呤的情况下，也能与相邻位置含有两个胞嘧啶类似物的寡核苷酸的硫醚和咪唑基团选择性反应，得到适合交联的铂化寡核苷酸。
