Synthesis, Gene Silencing, and Molecular Modeling Studies of 4′-C-Aminomethyl-2′-O-methyl Modified Small Interfering RNAs
摘要:
The linear syntheses of 4'-C-aminomethyl-2'-O-methyl uridine and cytidine nucleoside phosphoramidites were achieved using glucose as the starting material. The modified RNA building blocks were incorporated into small interfering RNAs (siRNAs) by employing solid phase RNA synthesis. Thermal melting studies showed that the modified siRNA duplexes exhibited slightly lower T-m (similar to 1 degrees C/modification) compared to the unmodified duplex. Molecular dynamics simulations revealed that the 4'-C-aminomethyl-2'-O-methyl modified nucleotides adopt South-type conformation in a siRNA duplex, thereby altering the stacking and hydrogen-bonding interactions. These modified siRNAs were also evaluated for their gene silencing efficiency in HeLa cells using a luciferase-based reporter assay. The results indicate that the modifications are well tolerated in various positions of the passenger strand and at the 3' end of the guide strand but are less tolerated in the seed region of the guide strand. The modified siRNAs exhibited prolonged stability in human serum compared to unmodified siRNA. This work has implications for the use of 4'-C-aminomethyl-2'-O-methyl modified nucleotides to overcome some of the challenges associated with the therapeutic utilities of siRNAs.
在本研究中,我们设计了4′- C-乙酰胺甲基-2′- O-甲氧基乙基(4′- C -ACM-2′- O -MOE)尿苷和胸苷修饰,旨在测试它们在小干扰RNA中的作用。热熔解研究表明,在 DNA 双链体中掺入单个 4'- C -ACM-2'- O -MOE 修饰会降低热稳定性。相反,当在 DNA:RNA 杂交体和 siRNA 中引入修饰时,观察到热稳定性增加。 DNA双链体的热失稳归因于不利的熵,这在一定程度上主要由焓因子补偿。在 3' 特异性核酸外切酶、蛇毒磷酸二酯酶 (SVPD) 存在下,dT 20 寡核苷酸 3' 末端倒数第二个位置上的单个 4'- C -ACM-2'- O -MOE 胸苷修饰显示出显着的修饰作用。与包括 2'- O -Me、2'- O -MOE 和 2'-F 在内的单体修饰相比,稳定性更高。在基因沉默研究中,我们发现过客链3'突出端的4'- C -ACM-2'- O