title: DNA-binding specificity of the IDI-4 basic leucine zipper factor of Podospora anserina defined by systematic evolution of ligands by exponential enrichment (SELEX).
abstract: Heterokaryon incompatibility is a cell destruction process that occurs when fungal cells of unlike genotype fuse. In Podospora anserina, autophagy is engaged during cell death by incompatibility and a number of genes are induced at the transcriptional level. These genes are termed idi (induced during incompatibility) genes. Among these is idi-4, a gene encoding a basic leucine zipper (bZIP) factor. IDI-4 displays similarity to the GCN4/cross-pathway control (CPC) factors that control gene expression in response to amino acid starvation in fungi. The overexpression of idi-4 triggers autophagy, leads to cell death, and also increases the expression of a number of idi genes, in particular idi-7, a gene involved in autophagy. Herein, we determined the in vitro target sequence of IDI-4. We have purified the recombinant IDI-4 bZIP domain and show that this 83-amino-acid-long peptide dimerizes in vitro and adopts an alpha-helical fold. We have then used a systematic evolution of ligands by exponential enrichment procedure to identify the sequence bound by the IDI-4 bZIP domain. The IDI-4 binding site consensus sequence corresponds to the ATGANTCAT pseudopalindrome. IDI-4 binding sites are present in the promoter region of the idi-7 gene, and the bZIP IDI-4 peptide binds to the idi-7 promoter in vitro. The identified IDI-4 consensus binding sequence is very similar to the GCN4/CPC binding site, raising the possibility of an interplay and/or partial functional redundancy between IDI-4 and CPC-type bZIP factors in fungi.
authors.affiliation: Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS-Université de Bordeaux 2, 33077 Bordeaux Cedex, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Dementhon
authors.forename: Sven J
authors.initials: SJ
authors.lastname: Saupe
mesh_terms: D000595:Amino Acid Sequence; D001343:Autophagy / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D016350:Leucine Zippers; D008024:Ligands; D008969:Molecular Sequence Data; D048468:Podospora / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D016415:Sequence Alignment
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D008024:Ligands