Isolation of the creA gene from the cellulolytic fungus Humicola grisea and analysis of CreA binding sites upstream from the cellulase genes

A carbon catabolite repressor gene, creA, was isolated from the cellulolytic fungus Humicola grisea by using a portion of the Trichoderma reesei cre1 gene as a probe. The deduced amino acid sequence predicts a zinc finger protein of 419 amino acids in length, and its zinc finger regions show high similarity with those of Aspergillus CreAs, T. reesei Cre1, and Saccharomyces cerevisiae MIG1. Northern blot analysis showed that the H. grisea creA gene was highly transcribed when the mycelia were grown on glucose-containing media, but the transcription of the H. grisea endoglucanase 1 gene (egl1) and the exoglucanase 1 gene (exo1) were repressed under these conditions. Results of binding assays with the maltose-binding protein::CreA(1-166) fusion protein and the egl1 and the exo1 upstream regions showed that some 6-bp sites having an identical or similar sequence to the consensus sequence for CreA binding were protected from DNase I digestion.