Three regulatory systems control expression of glutamine synthetase in Saccharomyces cerevisiae at the level of transcription.
The GLN1 gene of Saccharomyces cerevisiae was cloned by complementation of a gln1 auxotroph. A GLN1-lacZ fusion was constructed to assay GLN1 promoter activity. beta-Galactosidase and glutamine synthetase expression in chromosomally integrated GLN1-lacZ fusion strains were co-regulated in response to a shift from glutamine to glutamate as the nitrogen source, purine limitation, and 3-aminotriazole-induced histidine starvation. Regulation of GLN1 expression by each of the three pathways occurred at the transcriptional level. Increased accumulation of GLN1 mRNA was observed within 5 min after a shift from glutamine to glutamate as the nitrogen source. After 5 min, GLN1 mRNA levels were constant. The level of GLN1 transcript was reduced by approximately 75% within 5 min following glutamine addition to the cells growing with glutamate as nitrogen source. This indicates that the GLN1 message is unstable and has a half-life of approximately 3 min. Deletion analysis indicated that the sequences required for GLN1 expression are located within approximately 350 bp upstream from the transcriptional initiation site.
Benjamin
P M
PM
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Wu
J I
JI
Mitchell
A P
AP
Magasanik
B
B
D002872:Chromosome Deletion; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D005809:Genes, Regulator; D005974:Glutamate-Ammonia Ligase / Q000096:biosynthesis / Q000235:genetics*; D007763:Lac Operon; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
D005974:Glutamate-Ammonia Ligase