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Currently, several protein-based genetic determinants, or prions, are described in yeast, and several hundred prion candidates have been predicted. Importantly, many known and potential prion proteins regulate transcription; therefore, prion induction should affect gene expression. While it is generally believed that the prion phenotype should mimic the deletion phenotype, this rule has exceptions. Formed by the transcription factor Sfp1p, [ ISP+] is one such exception as the [ ISP+] and sfp1Δ strains differ in many phenotypic traits. These data suggest that effects of prion formation by a transcription factor and its absence may affect gene expression in a different way. However, studies addressing this issue are practically absent. Here, we explore how [ ISP+] affects gene expression and how these changes correspond to the effect of SFP1 deletion. Our data indicate that the [ ISP+]-related expression changes cannot be explained by the inactivation of Sfp1p. Remarkably, most Sfp1p targets are not affected in the [ ISP+] strain; instead, the genes upregulated in the [ ISP+] strain are enriched in Gcn4p and Aft1p targets. We propose that Sfp1p serves as a part of a regulatory complex, and the activity of this complex may be modulated differently by the absence or prionization of Sfp1p. [ABSTRACT FROM AUTHOR]

The Peterhof genetic collection of Saccharomyces cerevisiae strains (PGC) is a large laboratory stock that has accumulated several thousands of strains for over than half a century. It originated independently of other common laboratory stocks from a distillery lineage (race XII). Several PGC strains have been extensively used in certain fields of yeast research but their genomes have not been thoroughly explored yet. Here we employed whole genome sequencing to characterize five selected PGC strains including one of the closest to the progenitor, 15V-P4, and several strains that have been used to study translation termination and prions in yeast (25-25-2V-P3982, 1B-D1606, 74-D694, and 6P-33G-D373). The genetic distance between the PGC progenitor and S288C is comparable to that between two geographically isolated populations. The PGC seems to be closer to two bakery strains than to S288C-related laboratory stocks or European wine strains. In genomes of the PGC strains, we found several loci which are absent from the S288C genome; 15V-P4 harbors a rare combination of the gene cluster characteristic for wine strains and the RTM1 cluster. We closely examined known and previously uncharacterized gene variants of particular strains and were able to establish the molecular basis for known phenotypes including phenylalanine auxotrophy, clumping behavior and galactose utilization. Finally, we made sequencing data and results of the analysis available for the yeast community. Our data widen the knowledge about genetic variation between Saccharomyces cerevisiae strains and can form the basis for planning future work in PGC-related strains and with PGC-derived alleles. [ABSTRACT FROM AUTHOR]