Amino acid signaling in yeast: activation of Ssy5 protease is associated with its phosphorylation-induced ubiquitylation.

The yeast Ssy5 protein is a serine-type endoprotease autoprocessed into a catalytic domain and a large inhibitory prodomain. When external amino acids are detected by the plasma membrane Ssy1 sensor, Ssy5 is activated and catalyzes endoproteolytic processing of the Stp1 and Stp2 transcription factors. These Stp proteins then migrate into the nucleus and activate transcription of several amino acid permease genes.

Amino acid signaling in yeast: post-genome duplication divergence of the Stp1 and Stp2 transcription factors.

When yeast cells detect external amino acids via their permease-like Ssy1 sensor, the cytosolic precursor forms of Stp1 and Stp2 transcription factors are activated by endoproteolytic removal of their N-terminal domains, a reaction catalyzed by the Ssy5 endoprotease. The processed Stp factors then migrate into the nucleus, where they activate transcription of several amino acid permease genes including AGP1. We report here that the STP1 and STP2 genes most likely derive from the whole genome duplication that occurred in a yeast ancestor.

Effect of 21 different nitrogen sources on global gene expression in the yeast Saccharomyces cerevisiae.

We compared the transcriptomes of Saccharomyces cerevisiae cells growing under steady-state conditions on 21 unique sources of nitrogen. We found 506 genes differentially regulated by nitrogen and estimated the activation degrees of all identified nitrogen-responding transcriptional controls according to the nitrogen source. One main group of nitrogenous compounds supports fast growth and a highly active nitrogen catabolite repression (NCR) control.

Amino acid signaling in yeast: casein kinase I and the Ssy5 endoprotease are key determinants of endoproteolytic activation of the membrane-bound Stp1 transcription factor.

Saccharomyces cerevisiae cells possess a plasma membrane sensor able to detect the presence of extracellular amino acids and then to activate a signaling pathway leading to transcriptional induction of multiple genes, e.g., AGP1, encoding an amino acid permease.