Myung Hyun Jo1, 2, 3, 6, Soochul Shin1, 2, 3, 6, Seung-Ryoung Jung1, 2, 3, Eunji Kim5, Ji-Joon Song5,*, Sungchul Hohng1, 2, 3, 4,*
1Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
2 Institute of Applied Physics, Seoul National University, Seoul 151-747, Republic of Korea
3 National Center of Creative Research Initiatives, Seoul National University, Seoul 151-747, Republic of Korea
4 Department of Biophysics and Chemical Biology, Seoul National University, Seoul 151-747, Republic of Korea
5 Department of Biological Sciences, KI for the BioCentury, KAIST, Daejeon 305-338, Republic of Korea
6 Co-first author
*Corresponding author : Ji-Joon Song, Sungchul Hohng
Summary
Argonaute is a key enzyme of various RNA silencing pathways. We use single-molecule fluorescence measurements to characterize the reaction mechanisms of the core-RISC (RNA-induced silencing complex) composed of human Argonaute 2 and a small RNA. We found that target binding of core-RISC starts at the seed region, resulting in four distinct reaction pathways: target cleavage, transient binding, stable binding, and Argonaute unloading. The target cleavage requires extensive sequence complementarity and dramatically accelerates core-RISC recycling. The stable binding of core-RISC is efficiently established with the seed match only, providing a potential explanation for the seed-match rule of miRNA (microRNA) target selection. Target cleavage on perfect-match targets sensitively depends on RNA sequences, providing an insight into designing more efficient siRNAs (small interfering RNAs).