Abstract
The yeast Sup35 protein is a subunit of the translation termination factor, and its conversion to the [PSI+] prion state leads to more translational read-through. Although extensive studies have been done on [PSI+], changes at the proteomic level have not been performed exhaustively. We therefore used a SILAC-based quantitative mass spectrometry approach and identified 4187 proteins from both [psi−] and [PSI+] strains. Surprisingly, there was very little difference between the two proteomes under standard growth conditions. We found however that several [PSI+] strains harbored an additional chromosome, such as chromosome I. Albeit, we found no evidence to support that [PSI+] induces chromosomal instability (CIN). Instead we hypothesized that the selective pressure applied during the establishment of [PSI+]-containing strains could lead to a supernumerary chromosome due to the presence of the ade1-14 selective marker for translational read-through. We therefore verified that there was no prevalence of disomy among newly generated [PSI+] strains in absence of strong selection pressure. We also noticed that low amounts of adenine in media could lead to higher levels of mitochondrial DNA in [PSI+] in ade1-14 cells. Our study has important significance for the establishment and manipulation of yeast strains with the Sup35 prion.
Highlights
The mammalian prion protein is an infectious element capable of switching from its native fold into a distinct and stable structure, which can induce a similar conformational change to other mammalian prion proteins[1]
We verified by generation sequencing (NGS) that there was no prevalence of disomic cells when [PSI+] cells were isolated in the absence of strong selective pressure
We induced the formation of the Sup35 [PSI+] prion in [psi−]SILAC cells by overexpressing an exogenous Sup35NM fragment under a GAL promoter, following selection on SD − Ade plates containing arginine to produce the [PSI+]SILAC strain
Summary
The mammalian prion protein is an infectious element capable of switching from its native fold into a distinct and stable structure, which can induce a similar conformational change to other mammalian prion proteins[1]. It was proposed that the presence of [PSI+] in wild yeast populations could result from the positive selection for prions during rare occasions of extreme or rapidly changing environments, and is hypothesized to accelerate the capacity for evolutionary change by revealing hidden variation present past the stop codons[19] In this case, the presence of C-terminal extended polypeptides may potentially encode for proteins with enhanced functions in stress pathways. The presence of C-terminal extended polypeptides may potentially encode for proteins with enhanced functions in stress pathways These findings indicate that Sup[35] prions may have a detrimental effect on yeast survival in some environments, but continued to be maintained through selective positive pressure in times of rapid environmental change. We verified by generation sequencing (NGS) that there was no prevalence of disomic cells when [PSI+] cells were isolated in the absence of strong selective pressure
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