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 ded uced amino acid motif of the C-terminal region of jlbA encodes a putative D NA-binding site composed of a basic amino acid domain and an adjacent leuci ne zipper motif. This region shares highest similarities to the C-terminal DNA-binding domain and the basic zipper (bZIP)-motifs of transcription fact ors like CPCA from A. niger, Gcn4p from Saccharomyces cerevisiae, human JUN B and c-JUN. The putative jlbA protein contains a PEST-rich region (an inst ability 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 t he addition of the false feedback inhibitor 3-amino-1,2,4-triazole. This in duction is partially dependent and partially independent on the presence of the transcription factor CPCA. Therefore jlbA is a novel,gene of A. nidula ns which is transcriptionally activated by amino acid starvation conditions .