Yeast prions: could they be exaptations? The URE2/[URE3] system in Kluyveromyces lactis

• Published in: FEMS yeast research Vol. 11; no. 1; pp. 151 - 153
• Main Authors: Safadi, Rim Al, Talarek, Nicolas, Jacques, Noémie, Aigle, Michel
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.02.2011; Oxford University Press; Oxford University Press (OUP)
• Subjects: adaptation; Biochemistry, Molecular Biology; Cell Behavior; Cellular Biology; exaptation; Fungal Proteins - genetics; Fungal Proteins - metabolism; Genes, Reporter; Glutathione Peroxidase - genetics; Glutathione Peroxidase - metabolism; Kluyveromyces - enzymology; Kluyveromyces lactis; Life Sciences; Molecular biology; Mutants; Phenotype; Polymorphism, Genetic; prion; Prion protein; Prions - genetics; Prions - metabolism; Saccharomyces; Selection, Genetic; Sequence Deletion; Yeast; prion; adaptation; exaptation; Kluyveromyces lactis
• ISSN: 1567-1356; 1567-1364
• DOI: 10.1111/j.1567-1364.2010.00700.x

We examined aspects of the URE2/[URE3] prion system in Kluyveromyces lactis, which lies on a different evolutionary branch from Saccharomyces. We first analysed the polymorphism of the prion-forming domain in 38 strains. Considerable differences were found between these two genera, with little variation within K. lactis. We then analysed the regulatory function of Ure2p, using a deletion of URE2. We assessed the deregulation of two reporter genes: DAL5 and GDH2. Both were derepressed in the mutant strain, as in Saccharomyces. Finally, we tried to obtain the [URE3] prion from K. lactis. Despite the use of many different experimental conditions, we were unable to obtain a prion from Ure2p. This finding calls into question the extent to which the prion form of Ure2p may be considered an evolutionary adaptation, instead suggesting that an exaptation phenomenon may be more likely than a continuous selection history.