Ammonia Regulates VID30 Expression and Vid30p Function Shifts Nitrogen Metabolism toward Glutamate Formation Especially when Saccharomyces cerevisiae Is Grown in Low Concentrations of Ammonia

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The GATA family proteins Gln3p and Gat1p mediate nitrogen catabolite repression (NCR)-sensitive transcription in Saccharomyces cerevisiae. When cells are cultured with a good nitrogen source (glutamine, ammonia), Gln3p and Gat1p are restricted to the cytoplasm, whereas with a poor nitrogen source (proline), they localize to the nucleus, bind to the GATA sequences of NCR-sensitive gene promoters, and activate transcription. The target of rapamycin-signaling cascade and Ure2p participate in regulating the cellular localization of Gln3p and Gat1p. Rapamycin, a Tor protein inhibitor, like growth with a poor nitrogen source, promotes nuclear localization of Gln3p and Gat1p. gln3 Delta and ure2 Delta mutants are partially resistant and hypersensitive to growth inhibition by rapamycin, respectively. We show that a vid30 Delta is more rapamycin-sensitive than wild type but less so than a ure2 Delta. VID30 expression is modestly NCR-sensitive, responsive to deletion of URE2, and greatly increases in low ammonia medium. Patterns of gene expression in a vid30 Delta suggest that the Vid30p function shifts the balance of nitrogen metabolism toward the production of glutamate, especially when cells are grown in low ammonia. CAN1, DAL4, DAL5, MEP2, DAL1, DAL80, and GDH3 transcription is down-regulated by Vid30p function with proline as the nitrogen source. An effect, however, that could easily be indirect.