title: Promoter strength of folic acid synthesis genes affects sulfa drug resistance in Saccharomyces cerevisiae.
abstract: The enzyme dihydropteroate synthase (DHPS) is an important target for sulfa drugs in both prokaryotic and eukaryotic microbes. However, the understanding of DHPS function and the action of antifolates in eukaryotes has been limited due to technical difficulties and the complexity of DHPS being a part of a bifunctional or trifunctional protein that comprises the upstream enzymes involved in folic acid synthesis (FAS). Here, yeast strains have been constructed to study the effects of FOL1 expression on growth and sulfa drug resistance. A DHPS knockout yeast strain was complemented by yeast vectors expressing the FOL1 gene under the control of promoters of different strengths. An inverse relationship was observed between the growth rate of the strains and FOL1 expression levels. The use of stronger promoters to drive FOL1 expression led to increased sulfamethoxazole resistance when para-aminobenzoic acid (pABA) levels were elevated. However, high FOL1 expression levels resulted in increased susceptibility to sulfamethoxazole in pABA free media. These data suggest that up-regulation of FOL1 expression can lead to sulfa drug resistance in Saccharomyces cerevisiae.
authors.affiliation: CSIRO Health Sciences and Nutrition, Parkville, Victoria, Australia 3052. peter.iliades@csiro.au
authors.forename: Peter
authors.initials: P
authors.lastname: Iliades
authors.forename: Janette
authors.initials: J
authors.lastname: Berglez
authors.forename: Steven
authors.initials: S
authors.lastname: Meshnick
authors.forename: Ian
authors.initials: I
authors.lastname: Macreadie
mesh_terms: D010129:4-Aminobenzoic Acid / Q000494:pharmacology; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000494:pharmacology*; D003470:Culture Media; D004058:Diffusion; D004094:Dihydropteroate Synthase / Q000037:antagonists & inhibitors; D025141:Drug Resistance, Fungal; D004926:Escherichia coli / Q000235:genetics; D005492:Folic Acid / Q000096:biosynthesis* / Q000235:genetics*; D005822:Genetic Vectors; D008826:Microbial Sensitivity Tests; D009841:Oligonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics*; D013420:Sulfamethoxazole / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology*; D014169:Transformation, Bacterial; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D003470:Culture Media; D009841:Oligonucleotides; D013449:Sulfonamides; D005492:Folic Acid; D004094:Dihydropteroate Synthase; D001616:beta-Galactosidase; D013420:Sulfamethoxazole; D010129:4-Aminobenzoic Acid