ABSTRACT
CPCI, the principal regulatory protein required for cross-pathway control of amino acid biosynthetic genes in Neurospora crassa, contains a domain similar to the DNA-binding domain of GCN4, the corresponding general regulator in Saccharomyces cerevisiae. We examined binding by CPC1 synthesized in vitro and by CPC1 present in N. crassa whole-cell extracts. CPCI from both sources was shown to bind to the DNA sequence 5'-ATGACTCAT-3', which is also the preferred recognition sequence of GCN4, CPC1 was confirmed as the source of DNA-binding activity in extracts by immunoblotting. Slightly mobility differences between DNA complexes containing CPCI synthesized in vitro and CPC1 in mycelial extracts were observed. Analyses of N. crassa extracts from different stages of asexual development revealed that CPC1 was abundant immediately following spore germination and through early mycelial growth but was scarce subsequently. CPC1 levels could be increased at any time by imposing amino acid starvation. Copies of the CPC1 response element are located upstream of several genes regulated by cross-pathway control, including cpc-1 itself.
