[NSI+] determinant has a pleiotropic phenotypic manifestation that is modulated by SUP35, SUP45, and VTS1 genes.

We recently discovered the novel non-chromosomal determinant in Saccharomyces cerevisiae [NSI(+)] (nonsense suppression inducer), which causes omnipotent nonsense suppression in strains where the Sup35 N-terminal domain is deleted. [NSI(+)] possesses yeast prion features and does not correspond to previously identified yeast prion determinants. Here, we show that [NSI(+)] enhances nonsense codon read-through and inhibits vegetative growth in S. cerevisiae. Using a large-scale overexpression screen to identify genes that impact the phenotypic effects of [NSI(+)], we found that the SUP35 and SUP45 genes encoding the translation termination factors eRF3 and eRF1, respectively, modulate nonsense suppression in [NSI(+)] strains. The VTS1 gene encodes an NQ-enriched RNA-binding protein that enhances nonsense suppression in [NSI(+)] and [nsi(-)] strains. We demonstrate that VTS1 overexpression, like [NSI(+)] induction, causes translational read-through and growth defects in S. cerevisiae.