Dual influence of the yeast Cat1p (Snf1p) protein kinase on carbon source-dependent transcriptional activation of gluconeogenic genes by the regulatory gene CAT8.
The CSRE (carbon source-responsive element) is a sequence motif responsible for the transcriptional activation of gluconeogenic structural genes in Saccharomyces cerevisiae. We have isolated a regulatory gene, DIL1 (derepression of isocitrate lyase, = CAT8), which is specifically required for derepression of CSRE-dependent genes. Expression of CAT8 is carbon source regulated and requires a functional Cat1p (Snf1p) protein kinase. The derepression defect of CAT8 in a cat1 mutant could be suppressed by a mutant Mig1p repressor protein. Derepression of CAT8 also requires a functional HAP2 gene, suggesting a regulatory connection between respiratory and gluconeogenic genes. Carbon source-dependent protein-CSRE complexes detected in a gel retardation analysis with wild-type extracts were absent in cat8 mutant extracts. However, similar experiments with an epitope-tagged CAT8 gene product in the presence of tag-specific antibodies gave evidence against a direct binding of Cat8p to the CSRE. A constitutively expressed GAL4-CAT8 fusion gene revealed a carbon source-dependent transcriptional activation of a UAS(GAL)-containing reporter gene. Activation mediated by Cat8p was no longer detectable in a cat1 mutant. Thus, biosynthetic control of CAT8 as well as transcriptional activation by Cat8p requires a functional Cat1p protein kinase. A model proposing CAT8 as a specific activator of a transcription factor(s) binding to the CSRE is discussed.
Rahner
A
A
Institut für Mikrobiologie, Biochemie und Genetik, Lehrstuhl Biochemie, Universität Erlangen/Nürnberg, Erlangen, Germany.
Schöler
A
A
Martens
E
E
Gollwitzer
B
B
Schüller
H J
HJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002244:Carbon / Q000378:metabolism; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D015966:Gene Expression Regulation, Fungal; D005943:Gluconeogenesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
C092600:CAT8 protein, S cerevisiae; D004271:DNA, Fungal; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D002244:Carbon; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases