
pmid: 23184930
pmc: PMC3548494
Ure2 is a phosphoprotein and central negative regulator of nitrogen-responsive Gln3/Gat1 localization and their ability to activate transcription. This negative regulation is achieved by the formation of Ure2-Gln3 and -Gat1 complexes that are thought to sequester these GATA factors in the cytoplasm of cells cultured in excess nitrogen. Ure2 itself is a dimer the monomer of which consists of two core domains and a flexible protruding αcap. Here, we show that alterations in this αcap abolish rapamycin-elicited nuclear Gln3 and, to a more limited extent, Gat1 localization. In contrast, these alterations have little demonstrable effect on the Gln3 and Gat1 responses to nitrogen limitation. Using two-dimensional PAGE we resolved eight rather than the two previously reported Ure2 isoforms and demonstrated Ure2 dephosphorylation to be stimulus-specific, occurring after rapamycin treatment but only minimally if at all in nitrogen-limited cells. Alteration of the αcap significantly diminished the response of Ure2 dephosphorylation to the TorC1 inhibitor, rapamycin. Furthermore, in contrast to Gln3, rapamycin-elicited Ure2 dephosphorylation occurred independently of Sit4 and Pph21/22 (PP2A) as well as Siw14, Ptc1, and Ppz1. Together, our data suggest that distinct regions of Ure2 are associated with the receipt and/or implementation of signals calling for cessation of GATA factor sequestration in the cytoplasm. This in turn is more consistent with the existence of distinct pathways for TorC1- and nitrogen limitation-dependent control than it is with these stimuli representing sequential steps in a single regulatory pathway.
Sirolimus, Glutathione Peroxidase, Antifungal Agents, Saccharomyces cerevisiae Proteins, Nitrogen, Prions, Biochimie, Biologie moléculaire, Saccharomyces cerevisiae, GATA Transcription Factors, Protein Structure, Tertiary, Gene Expression Regulation, Fungal, Mutation, Biologie cellulaire, Signal Transduction, Transcription Factors
Sirolimus, Glutathione Peroxidase, Antifungal Agents, Saccharomyces cerevisiae Proteins, Nitrogen, Prions, Biochimie, Biologie moléculaire, Saccharomyces cerevisiae, GATA Transcription Factors, Protein Structure, Tertiary, Gene Expression Regulation, Fungal, Mutation, Biologie cellulaire, Signal Transduction, Transcription Factors
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