Single-molecule FRET uncovers hidden conformations and dynamics of human Argonaute 2

• Main Authors: Graus, V. (Author), Grohmann, D. (Author), Jakob, L. (Author), Kramm, K. (Author), Meister, G. (Author), Neumeier, J. (Author), Willkomm, S. (Author)
• Format: Article
• Language: English
• Published: Nature Research 2022
• Online Access: View Fulltext in Publisher

 Human Argonaute 2 (hAgo2) constitutes the functional core of the RNA interference pathway. Guide RNAs direct hAgo2 to target mRNAs, which ultimately leads to hAgo2-mediated mRNA degradation or translational inhibition. Here, we combine site-specifically labeled hAgo2 with time-resolved single-molecule FRET measurements to monitor conformational states and dynamics of hAgo2 and hAgo2-RNA complexes in solution that remained elusive so far. We observe dynamic anchoring and release of the guide’s 3’-end from the PAZ domain during the stepwise target loading process even with a fully complementary target. We find differences in structure and dynamic behavior between partially and fully paired canonical hAgo2-guide/target complexes and the miRNA processing complex formed by hAgo2 and pre-miRNA451. Furthermore, we detect a hitherto unknown conformation of hAgo2-guide/target complexes that poises them for target-directed miRNA degradation. Taken together, our results show how the conformational flexibility of hAgo2-RNA complexes determines function and the fate of the ribonucleoprotein particle. © 2022, The Author(s).