Induction of jlbA mRNA synthesis for a putative bZIP protein of Aspergillus nidulans by amino acid starvation

The jlbA (jun-like bZIP) gene of Aspergillus nidulans was isolated. The deduced amino acid motif of the C-terminal region of jlbA encodes a putative DNA-binding site composed of a basic amino acid domain and an adjacent leucine zipper motif. This region shares highest similarities to the C-terminal DNA-binding domain and the basic zipper (bZIP)-motifs of transcription factors like CPCA from A. niger, Gcn4p from Saccharomyces cerevisiae, human JUNB and c-JUN. The putative jlbA protein contains a PEST-rich region (an instability region rich in the an-Lino acids proline, glutamic acid, serine and threonine) described to be implicated in protein stability. The jlbA mRNA formation is elevated up to 40-fold upon amino acid starvation induced by the addition of the false feedback inhibitor 3-amino-1,2,4-triazole. This induction is partially dependent and partially independent on the presence of the transcription factor CPCA. Therefore jlbA is a novel,gene of A. nidulans which is transcriptionally activated by amino acid starvation conditions.