Ago蛋白结合向导链siRNA或miRNA形成的复合物是ＲＮＡ诱导的基因沉默符合物体的核心组分，序列特异性的识别之互补的mRNA，并将目的mRNA进行沉默。人们对siRNA利用碱基互补配对原则识别、结合靶链，以及Ａgo蛋白切割靶链的作用机理有了一定研究。但是，miRNA与靶链之间并不能完全互补配对，它们之间形成的突起和错配对结构和功能的影响还不清楚；另外，在基因沉默过程中Ago与向导链都将发生什么样的构象变化也需要进一步研究。本项目将运用X射线晶体学，并结合单分子和计算生物学方法，深入研究Ago-向导链-靶链复合物的结构与功能，分析不同部位的突起和错配对Ago 的活性与结构的影响，探讨除了种子区域的碱基互补配对原则之外，向导链识别靶链更详尽的机理，从而深入分析miRNA诱导基因沉默的机理；我们还将研究miRNA介导基因沉默过程中不同阶段Ago-miRNA-靶RNA复合物的构象变化的细节。

Argonaute (Ago) protein combined with small RNAs (siRNAs or miRNAs) is the key component of RNA-induced silencing complexes (RISCs). The small RNA works as the guide to identify the complementary target mRNAs, which is silenced by RISC via translational repression and degradation. How the siRNAs find their complete complementary target RNAs is well studied. However, bulge or mismatch will located inside the miRNA-target RNA duplex because many miRNAs are perfect complementary with target. How these bulges and mismatches are tolerated by Ago and the effect to Ago activity are still unclear. Moreover, the miRNA and Ago conformational change in RNA interference processes is need further studies. In this project, we will work on the structural and functional studies of Ago-guide strand-target strand complex. We will use part complementary (different base or position) desired guide strand for the specific target strand, together with Ago. Using X-ray diffraction, combined with cleavage activate, single-molecule techniques and computational biology to reveal the mechanism of Ago-miRNA-target RNA and the detail of their conformation changing during RNA silencing processes.