The Gln3 Transcriptional Regulator of Saccharomyces cerevisiae Manifests Prion-Like Properties upon Overproduction

Prions are proteins that can exist under the same conditions in two or more conformations, at least one of them is infectious. Usually, acquisition of infectious prion conformation is associated with the formation of amyloids-protein aggregates with a characteristic spatial structure. About 10 prions have been identified in the yeast Saccharomyces cerevisiae. The Gln3 protein, which is one of the key regulators of nitrogen metabolism in S. cerevisiae, contains an amyloidogenic region manifesting prion-like properties. The prion properties of the full-length Gln3 have not been studied. We have found that the amyloidogenic region of Gln3 acts as a template and initiates aggregation of the full-length Gln3 in the presence of the [PIN+] prion when Gln3 is overexpressed. Full-length Gln3 in its aggregated form manifests prion-like properties, including infectivity and dependence on the anti-prion agents; however, unlike other known yeast prions, prion-like state of Gln3 is observed only upon the protein overproduction. Here, we suggest the term conditional prions for proteins, whose prion state is maintained exclusively under non-physiological conditions.