Distinct phosphatase requirements and GATA factor responses to nitrogen catabolite repression and rapamycin treatment in S. cerevisiae

Abstract

The rapamycin (Rap) ‐sensitive TorC1 kinase complex and downstream phosphatases (Sit4, PP2A) are central components through which S. cerevisiae responds to its nutritional environment. TorC1 and the cell's internal nitrogen supply regulate the localization of Gln3 and Gat1, the transcriptional activators of Nitrogen Catabolite Repression (NCR) sensitive genes. In nitrogen excess, Gln3 and Gat1 are cytoplasmic and NCR‐sensitive transcription is repressed. During nitrogen limitation or Rap treatment, Gln3 and Gat1 are nuclear and transcription is derepressed. We have discovered distinct Sit4 and PP2A requirements for NCR‐sensitive and Rap‐induced nuclear Gat1 localization that differ markedly from those of Gln3. Our data suggest that Gln3 and Gat1 localizations are controlled by two separable but interconnected regulatory pathways receiving distinct input signals. Gln3 localization responds most strongly to intracellular nitrogen availability (NCR‐sensitive & methionine sulfoximine, Msx, induced) and more weakly to Rap inhibition of TorC1, whereas Gat1 localization responds most strongly to Rap‐inhibited TorC1 regulation and more weakly to NCR (insensitive to Msx). Supported by NIH grant GM‐35642‐22.