A mutation in a purported regulatory gene affects control of sterol uptake in Saccharomyces cerevisiae.
Aerobically growing wild-type strains of Saccharomyces cerevisiae are unable to take exogenously supplied sterols from media. This aerobic sterol exclusion is vitiated under anaerobic conditions, in heme-deficient strains, and under some conditions of impaired sterol synthesis. Mutants which can take up sterols aerobically in heme-competent cells have been selected. One of these mutations, designated upc2-1, gives a pleiotropic phenotype in characteristics as diverse as aerobic accumulation of sterols, total lipid storage, sensitivity to metabolic inhibitors, response to altered sterol structures, and cation requirements. During experiments designed to ascertain the effects of various cations on yeast with sterol alterations, it was observed that upc2-1 was hypersensitive to Ca2+. Using resistance to Ca2+ as a screening vehicle, we cloned UPC2 and showed that it is YDR213W, an open reading frame on chromosome IV. This belongs to a fungal regulatory family containing the Zn(II)2Cys6 binuclear cluster DNA binding domain. The single guanine-to-adenine transition in upc2-1 gives a predicted amino acid change from glycine to aspartic acid. The regulatory defect explains the semidominance and pleiotropic effects of upc2-1.
Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, USA.
J H
JH
Crowley
F W
FW
Leak
K V
KV
Shianna
S
S
Tove
L W
LW
Parks
D000595:Amino Acid Sequence; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics; D005800:Genes, Fungal; D005809:Genes, Regulator; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013261:Sterols / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D013261:Sterols; D015534:Trans-Activators; C113958:UPC2 protein, S cerevisiae; D002118:Calcium