A feature of the nitrogen regulatory circuit in filamentous fungi is that pathway-specific control genes mediate induction of enzymes by substrates in specific pathways. The gene encoding a new pathway-specific factor involving in purine degradation pathway - pco-1 was isolated from Neurospora using a PCR-mediated method. The open reading frame of the new factor gene is interrupted by two introns which were identified by comparing the genomic DNA sequence and the cDNA sequence obtained by RT-PCR. The predicted PCO1 protein contains 1101 amino acids and appears to possess a single Zn(II)2/Cys6 binuclear-type zinc cluster. A coiled-coil domain was predicted by computer-aided sequence analysis, suggesting that PCO1 might function as a dimer. A chemical crosslinking assay indicated PCO1 does dimerize in vitro. A loss of function pco-1 mutant was created by the rip procedure. Analysis of pco1- strains revealed that PCO1 acts as a positive regulator of the purine degradation pathway. Results of mobility shift assays indicate that PCO1 specifically binds to TCGG-N6-CCGA DNA sequences which exist in promoter regions of the structural genes it regulates. The C-terminus of PCO1 features a domain rich in glutamine, proline, isoleucine and acidic residues which are commonly found in activation domains of transcription factors. This domain shows higher homology to NIT4, the Neurospora pathway-specific factor in the nitrate assimilation pathway, than to UAY, its counterpart in Aspergillus nidulans, suggesting transcription factors in N. crassa may share similar activation regions.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference
- Fungal Genetics Conference 22nd (2001)