This misfolding cascade event is described by Watts et al. 6 as "epigenetic tem-plated protein misfolding", although the process by which one misfolded infectious prion protein initiates an alteration in the folding of an existing native prion protein remains unclear.
A distinctive property of the Sup35 conversion process in yeast is its dependence on the presence of a pre-existing prion, designated [ PIN+] for [ PSI+] inducibility factor (Derkatch et al., 1997).
An additional substitution created a strong transmission barrier against pre-existing prions.
FFI mice were highly resistant to infection by pre-existing prions, confirming infectivity did not arise from contaminating agents.
Understanding the risks that existing and emerging animal prion diseases pose will have direct translation to protecting public health.
"Films have included radiation as well as mutations of existing conditions such as prions, mad-cow disease, measles, and rabies," he said.
If a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, misfolded prion form; the prion acts as a template to guide the misfolding of more proteins into prion form.
Although they are not living organisms, these prion aggregates can self-propagate; when they enter a healthy organism, they cause existing, correctly folded proteins to adopt the prion fold.
Correspondingly, an affinity of Sse1 for the prion conformation of Sup35 would explain our observations; association of Sse1 with obligate [PSI+] conformational intermediates promotes conversion to the prion state, while binding of Sse1 to existing [PSI+] polymers would sterically hinder the curing by Hsp104 overproduction.
Finally, infectious prions can range down in size to oligomers of a few dozen prion protein molecules [18], which would be undetectable by existing biochemical methodologies including MS methods employed in this study.
