title: A paradoxical mutant GATA factor.
abstract: The niiA (nitrite reductase) and niaD (nitrate reductase) genes of Aspergillus nidulans are subject to both induction by nitrate and repression by ammonium or glutamine. The intergenic region between these genes functions as a bidirectional promoter. In this region, nucleosomes are positioned under nonexpression conditions. On nitrate induction under derepressing conditions, total loss of positioning occurs. This is independent of transcription and of the NirA-specific transcription factor but absolutely dependent on the wide-domain GATA-binding AreA factor. We show here that a 3-amino-acid deletion in the basic carboxy-terminal sequence of the DNA-binding domain results in a protein with paradoxical properties. Its weak DNA binding is consistent with its loss-of-function phenotype on most nitrogen sources. However, it results in constitutive expression and superinducibility of niiA and niaD. Nucleosome loss of positioning is also constitutive. The mutation partially suppresses null mutations in the transcription factor NirA. AreA binds NirA in vitro, and the mutation does not affect this interaction. The in vivo methylation pattern of the promoter is drastically altered, suggesting the recruitment of one or more unknown transcription factors and/or a local distortion on the DNA double helix.
authors.affiliation: Institut de Génétique et Microbiologie, Université Paris-Sud, UMR8621, 91405 Orsay Cedex, France.
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Muro-Pastor
authors.forename: Joseph
authors.initials: J
authors.lastname: Strauss
authors.forename: Ana
authors.initials: A
authors.lastname: Ramón
authors.forename: Claudio
authors.initials: C
authors.lastname: Scazzocchio
mesh_terms: D001665:Binding Sites; D002843:Chromatin / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D017930:Genes, Reporter; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics; D009566:Nitrates / Q000378:metabolism; D009572:Nitrite Reductases / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: C079728:AreA protein, Aspergillus nidulans; D002843:Chromatin; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009566:Nitrates; D014157:Transcription Factors; C071245:NirA protein, Aspergillus nidulans; D009565:Nitrate Reductases; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D001616:beta-Galactosidase