Alagia Adele, Terrazas Montserrat, Eritja Ramon
Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN Networking Centre on Bioengineering, Biomaterials and Nanomedicine, Jordi Girona 18-26, 08034 Barcelona, Spain.
Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac 10, 08028 Barcelona, Spain.
Molecules. 2015 Apr 24;20(5):7602-19. doi: 10.3390/molecules20057602.
The understanding of the mechanisms behind nucleotide recognition by Argonaute 2, core protein of the RNA-induced silencing complex, is a key aspect in the optimization of small interfering RNAs (siRNAs) activity. To date, great efforts have been focused on the modification of certain regions of siRNA, such as the 3'/5'-termini and the seed region. Only a few reports have described the roles of central positions flanking the cleavage site during the silence process. In this study, we investigate the potential correlations between the thermodynamic and silencing properties of siRNA molecules carrying, at internal positions, an acyclic L-threoninol nucleic acid (aTNA) modification. Depending on position, the silencing is weakened or impaired. Furthermore, we evaluate the contribution of mismatches facing either a natural nucleotide or an aTNA modification to the siRNA potency. The position 11 of the antisense strand is more permissive to mismatches and aTNA modification, in respect to the position 10. Additionally, comparing the ON-/OFF-target silencing of central mismatched siRNAs with 5'-terminal modified siRNA, we concluded: (i) central perturbation of duplex pairing features weights more on potency rather than silencing asymmetry; (ii) complete bias for the ON-target silencing can be achieved with single L-threoninol modification near the 5'-end of the sense strand.
对RNA诱导沉默复合体的核心蛋白AGO2识别核苷酸背后机制的理解，是优化小干扰RNA（siRNA）活性的关键方面。迄今为止，大量工作都集中在对siRNA某些区域的修饰上，比如3'/5'-末端和种子区域。仅有少数报道描述了切割位点侧翼中心位置在沉默过程中的作用。在本研究中，我们研究了在内部位置携带无环L-苏糖醇核酸（aTNA）修饰的siRNA分子的热力学性质与沉默性质之间的潜在相关性。根据位置不同，沉默作用会减弱或受损。此外，我们评估了与天然核苷酸或aTNA修饰相对的错配情况对siRNA效力的影响。相对于第10位，反义链的第11位对错配和aTNA修饰更具耐受性。另外，通过比较中心错配的siRNA与5'-末端修饰的siRNA的靶向/脱靶沉默情况，我们得出以下结论：（i）双链体配对特征的中心扰动对效力的影响大于对沉默不对称性的影响；（ii）在正义链5'-末端附近进行单个L-苏糖醇修饰可实现对靶向沉默的完全偏向性。
