title: A mutation in the Zn-finger of the GAL4 homolog LAC9 results in glucose repression of its target genes.
abstract: The transcriptional activator LAC9, a GAL4 homolog of Kluyveromyces lactis which mediates lactose and galactose-dependent activation of genes involved in the utilization of these sugars can also confer glucose repression to those genes. Here we report on the isolation and characterization of LAC9-2, an allele which encodes a glucose-sensitive activator in contrast to the one previously cloned. A single amino acid exchange of leu-104 to tryptophan is responsible for the glucose-insensitive phenotype. The mutation is located within the Zn-finger-like DNA binding domain which is highly conserved between LAC9 and GAL4. Glucose repression is also eliminated by duplication of the LAC9-2 allele. The data indicate that LAC9 is a limiting factor for beta-galactosidase gene expression under all growth conditions and that glucose reduces the activity of the activator.
authors.affiliation: Institute of Microbiology, Heinrich-Heine-Universität, Düsseldorf, FRG.
authors.forename: P
authors.initials: P
authors.lastname: Kuger
authors.forename: A
authors.initials: A
authors.lastname: Gödecke
authors.forename: K D
authors.initials: KD
authors.lastname: Breunig
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D004794:Enzyme Repression; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D005696:Galactosidases / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005947:Glucose / Q000494:pharmacology*; D007716:Kluyveromyces / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D008667:Metalloproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D011487:Protein Conformation; D015183:Restriction Mapping; D029701:Saccharomyces cerevisiae Proteins; D004718:Saccharomycetales / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D015032:Zinc / Q000378:metabolism*; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C058596:LAC9 protein, Kluyveromyces lactis; D008667:Metalloproteins; D015345:Oligonucleotide Probes; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D005696:Galactosidases; D001616:beta-Galactosidase; D005947:Glucose; D015032:Zinc