Abstract
Nitrogen replenishment of nitrogen-starved yeast cells resulted in substantial transcriptome changes. There was an unexplained rapid, transient down-regulation of glycolytic genes. This unexpected result prompted us to search for the factors controlling these changes, among which is the possible involvement of different nutrient-sensing pathways such as the TORC1 and cAMP/PKA pathways. To that end, the effects of various gene deletions or chemical blocking agents were tested by investigating the expression of PGK1, one of the glycolytic genes most affected after nitrogen replenishment. We report here that several factors affected glycolytic mRNA stability, among which were glucose sensing, protein elongation, nitrogen metabolism, and TOR signaling. Ammonium sensing was not involved in the response, but ammonium metabolism was required. Thus, our results suggest that, in the presence of glucose, carbon/nitrogen cross-talk is likely involved in the response to nitrogen upshift. Our data suggest that posttranscriptional control of glycolytic gene expression may be an important response to nitrogen replenishment.