Nitrogen catabolic gene expression in Saccharomyces cerevisiae has been reported to be regulated by three GATA family proteins, the positive regulators Gln3p and Gat1p/Nil1p and the negative regulator Dal80p/Uga43p. We show here that a fourth member of the yeast GATA family, the Dal80p homolog Deh1p, also negatively regulates expression of some, but not all, nitrogen catabolic genes, i.e., GAP1, DAL80, and UGA4 expression increases in a deh1 delta mutant. Consistent with Deh1p regulation of these genes is the observation that Deh1p forms specific DNA-protein complexes with GATAA-containing UGA4 and GAP1 promoter fragments in electrophoretic mobility shift assays. Deh1p function is demonstrable, however, only when a repressive nitrogen source such as glutamine is present; deh1 delta mutants exhibit no detectable phenotype with a poor nitrogen source such as proline. Our experiments also demonstrate that GATA factor gene expression is highly regulated by the GATA factors themselves in an interdependent manner. DAL80 expression is Gln3p and Gat1p dependent and Dal80p regulated. Moreover, Gln3p and Dal80p bind to DAL80 promoter fragments. In turn, GAT1 expression is Gln3p dependent and Dal80p regulated but is not autogenously regulated like DAL80. DEH1 expression is largely Gln3p independent, modestly Gat1p dependent, and most highly regulated by Dal80p. Paradoxically, the high-level DEH1 expression observed in a dal80::hisG disruption mutant is highly sensitive to nitrogen catabolite repression.
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