The REG1 gene product is required for repression of INO1 and other inositol-sensitive upstream activating sequence-containing genes of yeast.
A search was conducted for suppressors of the inositol auxotrophic phenotype of the ino4-8 mutant of yeast. The ino4-8 mutation is a single base pair change that results in substitution of lysine for glutamic acid at position 79 in the bHLH domain of the yeast regulatory protein, Ino4p. Ino4p dimerizes with a second bHLH protein, Ino2p, to form a complex that binds to the promoter of the INO1 gene, activating transcription. Of 31 recessive suppressors of ino4-8 isolated, 29 proved to be alleles of a single locus, identified as REG1, which encodes a regulatory subunit of a protein phosphatase involved in the glucose response pathway. The suppressor mutation, sia1-1, identified as an allele of REG1, caused constitutive INO1 expression and was capable of suppressing the inositol auxotrophy of a second ino4 missense mutant, ino4-26, as well as ino2-419, a missense mutation of INO2. The suppressors analyzed were unable to suppress ino2 and ino4 null mutations, but the reg1 deletion mutation could suppress ino4-8. A deletion mutation in the OPI1 negative regulator was incapable of suppressing ino4-8. The relative roles of the OPI1 and REG1 gene products in control of INO1 expression are discussed.
Ouyang
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Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Ruiz-Noriega
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Henry
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D051792:Basic Helix-Loop-Helix Proteins; D015152:Blotting, Northern; D002455:Cell Division; D004268:DNA-Binding Proteins; D004171:Diploidy; D005656:Fungal Proteins / Q000502:physiology*; D015870:Gene Expression; D017930:Genes, Reporter; D005838:Genotype; D016296:Mutagenesis; D020125:Mutation, Missense; D007296:Myo-Inositol-1-Phosphate Synthase / Q000502:physiology*; D010641:Phenotype; D010749:Phosphoprotein Phosphatases; D017354:Point Mutation; D054645:Protein Phosphatase 1; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic; D013997:Time Factors; D015534:Trans-Activators; D014157:Transcription Factors; D001616:beta-Galactosidase / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D007296:Myo-Inositol-1-Phosphate Synthase; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D001616:beta-Galactosidase; C095723:INO2 protein, S cerevisiae; C063311:INO4 protein, S cerevisiae; C070829:REG1 protein, S cerevisiae