The cpcA gene of the filamentous fungus Aspergillus nidulans encodes a protein of 245 amino acids in length with high similarity to the general amino acid control transcriptional activator Gcn4p of yeast which are able to complement each other. The mRNA level of cpcA is regulated under amino acid starvation resulting in a fourfold increase after eight hours of limitation. Deduced cpcA protein binding sites (GCRE's) in its own promoter imply a transcriptional autoregulation. Gel retardation assays showed binding activity of cpcAp in its promoter which was abolished when point mutations were integrated into the GCRE's. Two upstream open reading frames in the 5'region of the cpcA mRNA were identified suggesting an additional translational regulation. An increase of cpcA protein was observed to a factor of three after amino acid limitation. Deletion of cpcA causes a reduced growth rate to approximately 30% of wild-type. Additionally, cpcA mutant strains are unable to derepress general control regulated genes as trpC and argB resulting in an unability to grow under amino acid starvation conditions. Overexpression of cpcA results in a specific increased transcription of general control regulated genes. The sexual developmental program of A. nidulans cpcA overexpression strains was affected. High amounts of cpcA protein resulted in a block in cleistothecia formation at a defined timepoint and therefore in sterility. The same phenotype was observed after overexpression of the yeast GCN4 in A. nidulans. We suggest a function of the cpcA protein as general control transcriptional activator. In addition, overexpression of cpcA results in a direct or indirect manner in sexual sterility.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)