http://precedings.nature.com/users/fa11fdab10ff0dce65b0441a592412b8/ Documents posted by Steve Simoneau Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://precedings.nature.com/documents/3344/version/1 Unconventional infectious agents cause transmissible spongiform encephalopathy (TSE) diseases including scrapie and bovine spongiform encephalopathy (BSE) in animals and Creutzfeldt-Jakob disease in humans. The protein only hypothesis claims that the TSE agent is composed solely of the protein called prion (PrPsc)1. This protein is the misfolded form of a host-encoded cellular protein, PrPc exerting presumably a vital role at the synapse2. Even though now widely accepted, the prion concept fails to provide in certain circumstances3-6, a satisfying interpretation of the infectious phenomenon. Using the 263K scrapie-hamster model, we conducted a transmission study to search for a putative prion-associated factor indispensable for infectivity. Here we show that innocuous recombinant prion protein (recPrP) was capable, in a reproducible manner, of transmitting scrapie disease when the protein was β–sheet converted in a solution containing PrPsc-derived RNA material. Analysis of the PrP-RNA mixture revealed the association of recPrP with two prominent populations of small RNA molecules having an average length of about ~27 and ~55 nucleotides. We conclude that the nature of the TSE agent seems to be composed of a nucleoprotein molecular complex, in which informative RNA molecules of small sizes are associated with the misfolded prion protein (PrPsc). http://precedings.nature.com/documents/3344/version/1 Tue, 16 Jun 2009 14:48:42 UTC Small critical RNAs in the scrapie agent hdl:10101/npre.2009.3344.1 2009-06-16 Jean-Guy Fournier Nature Precedings 2009-06-16T14:48:42Z Manuscript Microbiology Neuroscience http://creativecommons.org/licenses/by/3.0/