SUP35 expression is enhanced in yeast containing [ISP+], a prion form of the transcriptional regulator Sfp1

• Published in: Prion 2011-10, Vol.5 (4), p.317-322
• Main Authors: Radchenko, Elina, Rogoza, Tatyana, Khokhrina, Maria, Drozdova, Polina, Mironova, Ludmila
• Format: Article
• Language: English
• Subjects: Research Paper
• ISSN: 1933-6896; 1933-690X
• DOI: 10.4161/pri.5.4.18426

[ ISP + ] is a prion form of the global transcriptional regulator Sfp1 in Saccharomyces cerevisiae that manifests phenotypically as an anti-suppressor of specific sup35 nonsense suppressor mutations. Although SUP35 is a Sfp1 target, the mechanism of anti-suppression is unclear. Here we show that the level of SUP35 transcription in [ ISP + ] cells containing the sup35 mutation is increased relative to [ isp − ] cells and cells with a SFP1 deletion. As a result, [ ISP + ] cells have increased amounts of Sup35 encoded by the mutant allele. Indeed, additional experiments showed that increased amounts of mutant Sup35 may cause anti-suppression. Remarkably, [ ISP + ] effects are not equivalent to those produced by SFP1 deletion, so [ ISP + ] represents an obvious example of a functionally active prion form of a protein. This feature distinguishes [ ISP + ] from other yeast prions, where prion switch often has the same effect as inactivation of a prion host gene. We suggest that enhancement of SUP35 expression in [ ISP + ] cells is caused by specific interaction of Sfp1 in its prion form with some negative SUP35 regulator. We also demonstrate that the advantage of [ ISP + ] strains over [ isp − ] strains described in our earlier work is specific for certain genetic background and growth conditions.