Importance of an N-terminal structural switch in the distinction between small RNA-bound and free ARGONAUTE

  • Nat Struct Mol Biol. 2025 Jan 7. doi: 10.1038/s41594-024-01446-9.
Simon Bressendorff  #  1 ,  Ida Marie Zobbe Sjøgaard  #  1 ,  Andreas Prestel  2 ,  Vasileios Voutsinos  3 ,  Martin D Jansson  4 ,  Patrice Ménard  4 ,  Anders H Lund  4 ,  Rasmus Hartmann-Petersen  3 ,  Birthe B Kragelund  2 ,  Christian Poulsen  1  5 ,  Peter Brodersen  6
Affiliations
  • 1. Copenhagen Plant Science Center, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
  • 2. Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
  • 3. Kaj Ulrik Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
  • 4. Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
  • 5. Novo Nordisk, Måløv, Denmark.
  • 6. Copenhagen Plant Science Center, Department of Biology, University of Copenhagen, Copenhagen, Denmark. [email protected].
  • # Contributed equally.
PMID: 39774835 DOI: 10.1038/s41594-024-01446-9
Abstract

ARGONAUTE (AGO) proteins bind to small non-coding RNAs to form RNA-induced silencing complexes. In the RNA-bound state, AGO is stable while RNA-free AGO turns over rapidly. Molecular features unique to RNA-free AGO that allow its specific recognition and degradation remain unknown. Here, we identify a confined, linear region in Arabidopsis AGO1 and human Ago2, the N-coil, as a structural switch with preferential accessibility in the RNA-free state. RNA-free Arabidopsis AGO1 interacts with the Autophagy cargo receptor ATI1 by direct contact with specific N-coil amino acid residues whose mutation reduces the degradation rate of RNA-free AGO1 in vivo. The N-coil of human Ago2 has similar degron activity dependent on residues in positions equivalent to those required for the Arabidopsis AGO1-ATI1 interaction. These results elucidate the molecular basis for specific recognition and degradation of the RNA-free state of eukaryotic AGO proteins.

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