CAAT binding factors positively regulating the expression of the amdS gene (encoding acetamidase) and two penicillin biosynthesis genes (ipnA and aatA) have been previously described in Aspergillus nidulans. The factors were called AnCF and PENRI respectively. Deletion of the hapC gene, encoding a protein with significant similarity to Hap3p of Saccharomyces cerevisiae, eliminated both AnCF and PENR1 binding activities. We now report the isolation of the genes hapB and hapE which encode proteins with central regions of high similarity to Hap2p and Hap5p of S. cerevisiae and to the CBF-B and CBF-C proteins of mammals. The HapB, HapC and HapE proteins have been shown to be necessary and sufficient for the formation of a CCAAT binding complex in vitro. Strains with deletions of each of the hapB, hapC and hapE genes have identical phenotypes of slow growth, poor conidiation and reduced expression of amdS. Furthermore, induction of amdS by omega amino acids, which is mediated by the AmdR pathway specific activator, is abolished in the hap deletion mutants as is growth on gamma-aminobutyric acid (GABA) as a sole nitrogen or carbon source. AmdR and AnCF bind to overlapping sites in the promoters of the amdS and gatA genes. It is known that AnCF can bind independently of AmdR. We suggest that AnCF binding is required for AmdR binding in vivo.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)