德州大学西南医学中心生物化学系，埃默里大学神经退行性疾病研究中心，人类遗传学系，霍华休斯医学研究所的科学家在RNAi效率研究方面取得新的进展，文章C3PO, an Endoribonuclease That Promotes RNAi by Facilitating RISC Activation发表在Science上。
文章通讯作者是1992年毕业于武汉大学的青年助理教授刘清华（qinghua Liu，生物通译），刘清华目前在德州大学西南医学中心生物化学系任助理教授一职。
双链RNA对基因表达的阻断作用被称为RNA干预（RNA interference, RNAi ）双链RNA经酶切后会形成很多小片段，称为siRNA，这些小片段一旦与信使RNA(mRNA)中的同源序列互补结合，会导致mRNA失去功能，即不能翻译产生蛋白质，也就是使基因“沉默”了。
在RNAi过程中，发挥重要作用的就是siRNA复合物（RISC），核糖核酸内切酶Argonaute和单链siRNA直接指导mRNA的切割.。
siRNA复合物（RISC）剪切示意图
刘清华等人在这次的研究中重新构建了长双链RNA和双链体siRNA，通过果蝇Dicer-2，R2D2和Ago2蛋白促进RISC发挥活性。
研究小组构建的这个促进RISC的调节因子名为C3PO，由Translin和Trax组成的复合物，是Mg2+离子依赖性的核糖核酸内切酶，它通过清除siRNA切割mRNA的残留物来提高RISC的效率。
这些研究结果表明，C3PO是一类可在体外试验中提高RNAi效率的RNAi重组系统蛋白。
赛业推荐原文检索
C3PO, an Endoribonuclease That Promotes RNAi by Facilitating RISC Activation
Ying Liu,1 Xuecheng Ye,1 Feng Jiang,1 Chunyang Liang,1 Dongmei Chen,2 Junmin Peng,2 Lisa N. Kinch,1,3 Nick V. Grishin,1,3 Qinghua Liu1,*
The catalytic engine of RNA interference (RNAi) is the RNA-induced silencing complex (RISC), wherein the endoribonuclease Argonaute and single-stranded small interfering RNA (siRNA) direct target mRNA cleavage. We reconstituted long double-stranded RNA– and duplex siRNA–initiated RISC activities with the use of recombinant Drosophila Dicer-2, R2D2, and Ago2 proteins. We used this core reconstitution system to purify an RNAi regulator that we term C3PO (component 3 promoter of RISC), a complex of Translin and Trax. C3PO is a Mg2+-dependent endoribonuclease that promotes RISC activation by removing siRNA passenger strand cleavage products. These studies establish an in vitro RNAi reconstitution system and identify C3PO as a key activator of the core RNAi machinery.
1 Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
2 Department of Human Genetics, Center for Neurodegenerative Diseases, Emory University, Atlanta, GA 30322, USA.
3 Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
