UGA4 gene encoding the gamma-aminobutyric acid permease in Saccharomyces cerevisiae is an acid-expressed gene.
OBJECTIVE
biological processes in all organisms are controlled by environmental conditions, however, information concerning the molecular responses to external pH is scarce. In this work we studied the pH response of UGA4 gene encoding delta-aminolevulinic acid and gamma-aminobutyric acid permease in Saccharomyces cerevisiae.


METHODS
we analyzed the effect of pH on the expression of UGA4 gene measuring beta-galactosidase activity in cells carrying a UGA4::lacZ fusion gene.


RESULTS
results indicate that UGA4 expression is higher at acidic pH. The expression of UGA3 and UGA35 genes, which encode two positive transcription factors, is not regulated by external pH, while the expression of UGA43 gene encoding a repressor of UGA4 transcription is dependent on pH. Using a strain lacking Uga43p we clearly showed that the effect of ambient pH on UGA4 expression is not a secondary effect of the pH regulation on UGA43. We have also demonstrated that the effect of pH can only be detected when UGA4 gene is not subject to a strong repression by Uga43p nor to GABA induction.


CONCLUSIONS
here, we demonstrate that UGA4 is an acid-expressed gene. This regulation is probably mediated by Rim101p through the consensus site 5'-GCCARG-3' at 237 bp preceding the UGA4 coding sequence (201).
Moretti
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MB
Centro de Investigaciones sobre Porfirinas y Porfirias. CIPYP (CONICET, FCEyN, UBA), Ciudad Universitaria, Pabellón II, 2nd Piso, (1428), Buenos Aires, Argentina.
Batlle
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A
Garcia
S C
SC
D000622:Aminolevulinic Acid / Q000378:metabolism; D001665:Binding Sites; D050485:GABA Plasma Membrane Transport Proteins; D006863:Hydrogen-Ion Concentration; D007763:Lac Operon; D027361:Organic Anion Transporters / Q000096:biosynthesis* / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D001616:beta-Galactosidase / Q000378:metabolism
D050485:GABA Plasma Membrane Transport Proteins; D027361:Organic Anion Transporters; D029701:Saccharomyces cerevisiae Proteins; C513599:UGA4 protein, S cerevisiae; D000622:Aminolevulinic Acid; D001616:beta-Galactosidase