Report explores mechanisms underlying target cleavage by RISC

Yao C, Sasaki HM, Ueda T, Tomari Y, Tadakuma H. Single-Molecule Analysis of the Target Cleavage Reaction by the Drosophila RNAi Enzyme Complex. Mol Cell. 2015 Jul 2;59(1):125-32. PMID: 26140368.

From the abstract: "Small interfering RNAs (siRNAs) direct cleavage of complementary target RNAs via an RNA-induced silencing complex (RISC) that contains Argonatute2 protein at its core. However, what happens after target cleavage remains unclear. Here we analyzed the cleavage reaction by Drosophila Argonaute2-RISC using single-molecule imaging and revealed a series of intermediate states in target recognition, cleavage, and product release. Our data suggest that, after cleavage, RISC generally releases the 5' cleavage fragment from the guide 3' supplementary region first and then the 3' fragment from the seed region, highlighting the reinforcement of the seed pairing in RISC. ... "