The QUTA activator and QUTR repressor proteins of Aspergillus nidulans interact to regulate transcription of the quinate utilization pathway genese.
Genetic evidence suggests that the activity of the native QUTA transcription activator protein is negated by the action of the QUTR transcription repressor protein. When Aspergillus nidulans was transformed with plasmids containing the wild-type qutA gene, transformants that constitutively expressed the quinate pathway enzymes were isolated. The constitutive phenotype of these transformants was associated with an increased copy number of the transforming qutA gene and elevated qutA mRNA levels. Conversely, when A. nidulans was transformed with plasmids containing the qutR gene under the control of the constitutive pgk promoter, transformants with a super-repressed phenotype (unable to utilize quinate as a carbon source) were isolated. The super-repressed phenotype of these transformants was associated with an increased copy number of the transforming qutR gene and elevated qutR mRNA levels. These copy-number-dependent phenotypes argue that the levels of the QUTA and QUTR proteins were elevated in the high-copy-number transformants. When diploid strains were formed by combining haploid strains that contained high copy numbers of either the qutA gene (constitutive phenotype) or the qutR gene (super-repressing; non-inducible phenotype), the resulting diploid phenotype was one of quinate-inducible production of the quinate pathway enzymes, in a manner similar to wild-type. The simplest interpretation of these observations is that the QUTR repressor protein mediates its repressing activity through a direct interaction with the QUTA activator protein. Other possible interpretations are discussed in the text. Experiments in which truncated versions of the QUTA protein were produced in the presence of a wild-type QUTA protein indicate that the QUTR repressor protein recognizes and binds to the C-terminal half of the QUTA activator protein.
Lamb
Heather K
HK
Department of Biochemistry and Genetics, Medical School, Framlington Place, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
Newton
Giles H
GH
Department of Biochemistry and Genetics, Medical School, Framlington Place, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
Levett
Lisa J
LJ
Department of Biochemistry and Genetics, Medical School, Framlington Place, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
Cairns
Elaine
E
Department of Biochemistry and Genetics, Medical School, Framlington Place, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
Roberts
Clive F
CF
Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
Hawkins
Alastair R
AR
Department of Biochemistry and Genetics, Medical School, Framlington Place, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D001233:Aspergillus nidulans / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004171:Diploidy; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005822:Genetic Vectors / Q000235:genetics; D006238:Haploidy; D006836:Hydro-Lyases / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011801:Quinic Acid / Q000378:metabolism*; D012331:RNA, Fungal / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014170:Transformation, Genetic
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C098152:QutA protein, Aspergillus nidulans; D012331:RNA, Fungal; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D011801:Quinic Acid; D000429:Alcohol Oxidoreductases; C022511:quinate dehydrogenase; C044921:3-dehydroshikimate dehydratase; D006836:Hydro-Lyases; C020000:3-dehydroquinate dehydratase