Abstract
Eukaryotic release factors 1 and 3, encoded by SUP45 and SUP35, respectively, in Saccharomyces cerevisiae, are required for translation termination. Recent studies have shown that, besides these two key factors, several genetic and epigenetic mechanisms modulate the efficiency of translation termination. These mechanisms, through modifying translation termination fidelity, were shown to affect various cellular processes, such as mRNA degradation, and in some cases could confer a beneficial phenotype to the cell. The most studied example of such a mechanism is [PSI+], the prion conformation of Sup35p, which can have pleiotropic effects on growth that vary among different yeast strains. However, genetic loci underlying such readthrough-dependent, background-specific phenotypes have yet to be identified. Here, we used sup35C653R, a partial loss-of-function allele of the SUP35 previously shown to increase readthrough of stop codons and recapitulate some [PSI+]-dependent phenotypes, to study the genetic basis of phenotypes revealed by increased translational readthrough in two divergent yeast strains: BY4724 (a laboratory strain) and RM11_1a (a wine strain). We first identified growth conditions in which increased readthrough of stop codons by sup35C653R resulted in different growth responses between these two strains. We then used a recently developed linkage mapping technique, extreme QTL mapping (X-QTL), to identify readthrough-dependent loci for the observed growth differences. We further showed that variation in SKY1, an SR protein kinase, underlies a readthrough-dependent locus observed for growth on diamide and hydrogen peroxide. We found that the allelic state of SKY1 interacts with readthrough level and the genetic background to determine growth rate in these two conditions.
Highlights
High fidelity in translation, one of the key steps in the expression of genetic information, is essential for functional integrity of the cell
Sup35p carries an intrinsically disordered prion-determining region at its amino terminus. When this domain switches to the aggregating amyloid conformation, much of the protein becomes unavailable for translation terminations, which in turn increases readthrough of stop codons [7,8]. [PSI+] was reported to generate different phenotypes in different genetic backgrounds, and most of these phenotypic effects were shown to be recapitulated by a partial lossof-function allele of SUP35, sup35C653R [9]
We showed that variants in the gene SKY1 underlie one of the loci detected for readthroughdependent growth phenotypes in the presence of two chemicals that induce oxidative stress
Summary
One of the key steps in the expression of genetic information, is essential for functional integrity of the cell. Recent studies of translation termination in Saccharomyces cerevisiae have revealed genetic and epigenetic regulatory mechanisms that modify translation termination efficiency, which can affect cellular processes such as mRNA degradation and, in some cases, can confer a beneficial phenotype to the cell [4]. The most studied example of such mechanisms is the yeast prion [PSI+], which is formed by a conformational change in Sup35p, a subunit of the translation termination complex [5]. Sup35p carries an intrinsically disordered prion-determining region at its amino terminus. When this domain switches to the aggregating amyloid conformation (the prion conformation), much of the protein becomes unavailable for translation terminations, which in turn increases readthrough of stop codons [7,8]. When this domain switches to the aggregating amyloid conformation (the prion conformation), much of the protein becomes unavailable for translation terminations, which in turn increases readthrough of stop codons [7,8]. [PSI+] was reported to generate different phenotypes in different genetic backgrounds, and most of these phenotypic effects were shown to be recapitulated by a partial lossof-function allele of SUP35, sup35C653R [9]
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