Biological and physicochemical characterization of siRNAs modified with 2′,2′-difluoro-2′-deoxycytidine (gemcitabine)
作者:Malgorzata Sierant、Milena Sobczak、Magdalena Janicka、Alina Paduszynska、Danuta Piotrzkowska
DOI:10.1039/b9nj00746f
日期:——
The use of synthetic short interfering RNAs (siRNAs) is currently a method of choice to manipulate gene expression in mammalian cells. Efforts aimed at improving siRNA biological activity, including increased silencing properties, higher substrate specificity and cellular stability, lower cytotoxicity, and improved target delivery, have been made through the introduction of various chemical modifications into the siRNA strands. In these studies, we present the synthesis of oligoribonucleotides with the single replacement of a cytidine unit for 2â²,2â²-difluoro-2â²-deoxycytidine (gemcitabine, dFdC) and the use of them in a series of siRNAs for gene silencing experiments. The dFdC modifications are located in six different positions of the antisense strand, which are crucial for siRNA silencing activity. The results indicate a position-dependent tolerance for the dFdC modification. Gemcitabine units present in the âseed regionâ, at positions 1 or 8, resulted in only a â¼15% silencing activity in the corresponding duplexes. The dFdC unit at position 10 virtually switched off the silencing activity (below 10%), while the dFdC unit at the positions 2, 4 or 5 produced duplexes of silencing potential comparable to that of the non-modified duplex (70% silencing). The dFdC modification had little impact on the structure of the siRNA duplexes, as determined by circular dichroism analysis, while melting experiments showed their lower thermal stability.
目前,使用合成短干扰 RNA(siRNA)是操纵哺乳动物细胞基因表达的首选方法。人们通过在 siRNA 链中引入各种化学修饰,努力提高 siRNA 的生物活性,包括增强沉默特性、提高底物特异性和细胞稳定性、降低细胞毒性以及改善靶向传递。在这些研究中,我们介绍了用 2â²,2â²-二氟-2â²-脱氧胞苷(gemcitabine,dFdC)替换一个胞苷单位的寡核苷酸的合成,并将其用于一系列 siRNA 的基因沉默实验。dFdC 修饰位于反义链的六个不同位置,这些位置对 siRNA 的沉默活性至关重要。结果表明,dFdC 修饰的耐受性与位置有关。位于 "种子区 "第1位或第8位的吉西他滨单位在相应的双链中只产生了¼15%的沉默活性。位于第 10 位的 dFdC 单元实际上关闭了沉默活性(低于 10%),而位于第 2、4 或 5 位的 dFdC 单元产生的双链体的沉默潜力与未修饰的双链体相当(70% 的沉默)。圆二色性分析表明,dFdC 修饰对 siRNA 双链体的结构影响很小,而熔化实验则表明它们的热稳定性较低。