A global investigation of gene deletion strains that affect premature stop codon bypass in yeast, Saccharomyces cerevisiae.

Protein biosynthesis is an orderly process that requires a balance between rate and accuracy. To produce a functional product, the fidelity of this process has to be maintained from start to finish. In order to systematically identify genes that affect stop codon bypass, three expression plasmids, pUKC817, pUKC818 and pUKC819, were integrated into the yeast non-essential loss-of-function gene array (5000 strains). These plasmids contain three different premature stop codons (UAA, UGA and UAG, respectively) within the LacZ expression cassette. A fourth plasmid, pUKC815 that carries the native LacZ gene was used as a control. Transformed strains were subjected to large-scale β-galactosidase lift assay analysis to evaluate production of β-galactosidase for each gene deletion strain. In this way 84 potential candidate genes that affect stop codon bypass were identified. Three candidate genes, OLA1, BSC2, and YNL040W, were further investigated, and were found to be important for cytoplasmic protein biosynthesis.