9W5I

AGO maturation complex (AMC): AGO2-miRNA duplex in complex with Hsp90 beta and co-chaperone p23

Summary for 9W5I

• Entry DOI: 10.2210/pdb9w5i/pdb
• EMDB information: 65663
• Descriptor: Heat shock protein HSP 90-beta, Prostaglandin E synthase 3, Protein argonaute-2, ... (7 entities in total)
• Functional Keywords: hsp90, p23, argonaute, mirna, ago2, chaperone, co-chaperone
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 6
• Total formula weight: 297883.58

Authors

Lee, H.,Jeong, M.-S.,Lee, Y.-Y.,Lee, J.-H.,Lee, D.,Kim, V.N.,Roh, S.-H. (deposition date: 2025-08-01, release date: 2026-04-22, Last modification date: 2026-07-01)

Primary citation

Lee, Y.Y.,Jeong, M.,Lee, H.,Lee, D.,Lee, J.,Park, J.,Kim, V.N.,Roh, S.H.
Structural basis for chaperone-guided assembly of RNA-induced silencing complex.
Nature, 2026

PubMed Abstract: The RNA-induced silencing complex (RISC), comprising an Argonaute (AGO) protein and a small RNA, is the central effector in RNA silencing. Small RNAs are loaded onto AGO as bulky duplexes in an HSP70- and HSP90-dependent process, but the molecular mechanism remains poorly understood. Here we identify the human AGO-HSP90-p23 complex, which captures AGO in an RNA-free state, termed the AGO maturation complex (AMC). The purified AMC enables RNA loading and AGO folding, faithfully recapitulating de novo RISC assembly. Using cryogenic electron microscopy, we determined the structure of AMC bound to a microRNA duplex. In contrast to its conformation in the RISC, AGO adopts a highly open conformation in the AMC: the N domain and the RNA-binding module (PAZ-MID-PIWI) are fully detached and anchored to opposite sides of the HSP90 dimer, connected solely by the unfolded L1 linker. This arrangement exposes a positively charged cleft that accommodates an RNA duplex. AGO folding is facilitated by a small RNA duplex containing a 5'-terminal phosphate-but not by single-stranded RNAs-revealing a role for the RNA duplex as a chaperone-like cofactor that directs AGO domain assembly. These findings elucidate the RISC assembly mechanism and establish the AMC as a molecular tool for probing optimal RNA features and chemical modifications for the rational design of small interfering RNA therapeutics. Our study also sheds light on how chaperones, together with ligands, can guide the folding of client proteins.

PubMed: 42271054
DOI: 10.1038/s41586-026-10640-2

Experimental method

ELECTRON MICROSCOPY (2.63 Å)