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Updated: Apr 17, 2026

Investigating the Spreading and Toxicity of Prion-like Proteins Using the Metazoan Model Organism C. elegans
Published on: January 8, 2015
Feedback control of prion formation and propagation by the ribosome-associated chaperone complex
Denis A Kiktev1, Mikhail M Melomed, Caroline D Lu
1School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA; Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia.
Abstract:
Cross-beta fibrous protein aggregates (amyloids and amyloid-based prions) are found in mammals (including humans) and fungi (including yeast), and are associated with both diseases and heritable traits. The Hsp104/70/40 chaperone machinery controls propagation of yeast prions. The Hsp70 chaperones Ssa and Ssb show opposite effects on [PSI(+)], a prion form of the translation termination factor Sup35 (eRF3). Ssb is bound to translating ribosomes via ribosome-associated complex (RAC), composed of Hsp40-Zuo1 and Hsp70-Ssz1. Here we demonstrate that RAC disruption increases de novo prion formation in a manner similar to Ssb depletion, but interferes with prion propagation in a manner similar to Ssb overproduction. Release of Ssb into the cytosol in RAC-deficient cells antagonizes binding of Ssa to amyloids. Thus, propagation of an amyloid formed because of lack of ribosome-associated Ssb can be counteracted by cytosolic Ssb, generating a feedback regulatory circuit. Release of Ssb from ribosomes is also observed in wild-type cells during growth in poor synthetic medium. Ssb is, in a significant part, responsible for the prion destabilization in these conditions, underlining the physiological relevance of the Ssb-based regulatory circuit.
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