Prion protein gene polymorphisms in Saccharomyces cerevisiae

Area of Science:

• * Molecular biology
• * Yeast genetics
• * Evolutionary biology

Background:

• * Yeast Saccharomyces cerevisiae possesses proteins capable of forming stable, transmissible prions.
• * Prion formation depends on intact prion-forming domains (PrDs), rich in Asn/Gln residues.
• * The evolutionary significance of these prion properties is not fully understood.

Purpose of the Study:

• * To investigate the evolutionary significance of prion protein domains in natural yeast strains.
• * To analyze genetic variations in key prion genes (SUP35, RNQ1, URE2, NEW1) across different S. cerevisiae isolates.
• * To identify potential genetic mechanisms underlying prion variability and adaptation.

Main Methods:

• * Comparative analysis of prion gene sequences (SUP35, RNQ1, URE2, NEW1) from 16 natural Saccharomyces cerevisiae strains.
• * Identification and characterization of gene alleles and polymorphisms, particularly within prion-forming domains.
• * Investigation of the association between identified polymorphisms and DNA tandem repeat variations.

Main Results:

• * A novel SUP35 allele (SUP35delta19) with a 19-amino acid deletion in the PrD was found in 4 out of 16 strains, abolishing prion formation.
• * The RNQ1 gene exhibited high polymorphism, with eight different alleles detected in six diploid strains.
• * URE2 and NEW1 genes showed no significant DNA polymorphism, indicating differential evolutionary pressures on prion genes.

Conclusions:

• * Genetic variations, including deletions and polymorphisms in prion genes like SUP35 and RNQ1, are present in natural yeast populations.
• * DNA tandem repeat expansions and contractions within RNQ1 may facilitate rapid switching between prion and non-prion states.
• * These findings suggest that prion systems in yeast are subject to evolutionary forces driving adaptability and variation.