title: Characterization of genes that are synthetically lethal with ade3 or leu2 in Saccharomyces cerevisiae.
abstract: Combinations of two non-lethal mutations that result in cell death are synthetically lethal. Such a genetic relationship suggests a functional interaction between the corresponding gene products. Frequently, an ade2 ade3 colony-sectoring assay is used to screen for synthetic lethal mutants. In these screens, mutants are sought that fail to lose a plasmid that bears a gene of interest. However, a subset of mutants is often found that is dependent on plasmid components other than the target gene. To understand the mechanism of this dependence, we characterized those mutants that, although prevalent in most mutant hunts, are usually discarded. Using a LEU2-ADE3 plasmid, plasmid-dependent mutations were found in the SHM2, PTR3, BAP2 and SSY1 genes. Double shm2 ade3 mutants are non-viable because the two pathways for tetrahydrofolate synthesis are blocked. Mutations in PTR3, BAP2 and SSY1 disrupt sensing and transport of extracellular leucine. Therefore, ptr3, bap2 or ssy1 mutants must be leucine prototrophs to grow on rich media. In light of these findings, we propose modifications that should improve the efficiency of synthetic lethal screening procedures.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Missouri-Columbia, Columbia, MO 65212, USA.
authors.forename: Shraddha S
authors.initials: SS
authors.lastname: Nigavekar
authors.forename: John F
authors.initials: JF
authors.lastname: Cannon
mesh_terms: D050539:3-Isopropylmalate Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000235:genetics*; D000619:Aminohydrolases / Q000235:genetics*; D005574:Formate-Tetrahydrofolate Ligase / Q000235:genetics*; D005800:Genes, Fungal; D005804:Genes, Lethal; D005821:Genetic Techniques; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000235:genetics*; D009097:Multienzyme Complexes / Q000235:genetics*; D009154:Mutation; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*
chemical_list: D009097:Multienzyme Complexes; C021836:formyl-methenyl-methylenetetrahydrofolate synthetase; D000429:Alcohol Oxidoreductases; D050539:3-Isopropylmalate Dehydrogenase; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D000619:Aminohydrolases; D005574:Formate-Tetrahydrofolate Ligase