Contribution of Cat8 and Sip4 to the transcriptional activation of yeast gluconeogenic genes by carbon source-responsive elements.
The carbon source-responsive element (CSRE) functions as an activating promoter motif of gluconeogenic genes in Saccharomyces cerevisiae. The positively acting regulatory genes CAT8 and SIP4 encode CSRE-binding proteins which contribute unequally to the regulated expression of a CSRE-dependent reporter gene (85% and 15%, respectively, under conditions of glucose derepression). Deregulated variants of Cat8 and Sip4 are able to bind to the CSRE and allow glucose-insensitive gene activation, even in the absence of the other protein, arguing against the physiological significance of heterodimer formation. Gel retardation assays provide evidence for a different binding affinity of Cat8 and Sip4 to at least some CSRE sequence variants. Both efficient biosynthesis of and transcriptional activation by Sip4 require a functional CAT8 gene, while Cat8 was not dependent on SIP4. Thus, our data suggest that the apparent minor importance of Sip4 may be the result of autoregulatory cross-talk among the isofunctional activators Cat8 and Sip4. The derepression deficiency of a CSRE-dependent reporter gene in a strain lacking the Cat1 (Snf1) protein kinase can be suppressed by Sip4 fused to a strong heterologous activation domain. This finding agrees with the idea that phosphorylation by Cat1 may convert Sip4 into a functional activator.
Hiesinger
M
M
Institut für Genetik und Biochemie, Ernst-Moritz-Arndt-Universität, Jahnstrasse 15a, 17487 Greifswald, Germany.
Roth
S
S
Meissner
E
E
Schüller
H J
HJ
D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D002244:Carbon / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018628:Gene Dosage; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D005800:Genes, Fungal / Q000235:genetics; D017930:Genes, Reporter; D014644:Genetic Variation; D005838:Genotype; D005943:Gluconeogenesis / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D020218:Response Elements / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation
D050976:Basic-Leucine Zipper Transcription Factors; C092600:CAT8 protein, S cerevisiae; D005656:Fungal Proteins; C099279:SIP4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D002244:Carbon