Influence of gene dosage and autoregulation of the regulatory genes INO2 and INO4 on inositol/choline-repressible gene transcription in the yeast Saccharomyces cerevisiae.
Expression of structural genes of phospholipid biosynthesis in yeast is mediated by the inositol/choline-responsive element (ICRE). ICRE-dependent gene activation, requiring the regulatory genes INO2 and INO4, is repressed in the presence of the phospholipid precursors inositol and choline. INO2 and, to a less extent, INO4 are positively autoregulated by functional ICRE sequences in the respective upstream regions. However, an INO2 allele devoid of its ICRE functionally complemented an ino2 mutation and completely restored inositol/choline regulation of Ino2p-dependent reporter genes. Low-level expression of INO2 and INO4 genes, each under control of the heterologous MET25 promoter, did not alter the regulatory pattern of target genes. Thus, upstream regions of INO2 and INO4 are not crucial for transcriptional control of ICRE-dependent genes by inositol and choline. Interestingly, over-expression of INO2, but not of INO4, counteracted repression by phospholipid precursors. Possibly, a functional antagonism between INO2 and a negative regulator is the key event responsible for repression or de-repression.
Schwank
S
S
Institut für Mikrobiologie, Biochemie und Genetik, Lehrstuhl Biochemie, Universität Erlangen/Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany.
Hoffmann
B
B
Sch-uller
H J
HJ
D051792:Basic Helix-Loop-Helix Proteins; D002794:Choline / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D015966:Gene Expression Regulation, Fungal; D006706:Homeostasis; D007294:Inositol / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D051792:Basic Helix-Loop-Helix Proteins; D002794:Choline; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D007294:Inositol; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C095723:INO2 protein, S cerevisiae; C063311:INO4 protein, S cerevisiae; C096105:OPI1 protein, S cerevisiae