CARBON CATABOLITE REPRESSION IN ASPERGILLUS-NIDULANS - A REVIEW

We describe the experimental methodology that led to the discovery of the creA gene in Aspergillus nidulans. This gene codes for a transcrip tional repressor mediating carbon catabolite repression in many pathwa ys in this organism. We compare both the mode and the mechanism of act ion in two pathways subject to CreA-mediated repression. The genes com prising the ethanol regulon are subject to carbon catabolite repressio n independently of the nitrogen source, while the genes involved in pr oline utilization are repressed by glucose only when a repressing nitr ogen source is also present. In the ethanol regulon, CreA drastically represses the expression of the positive regulatory gene alcR, thus pr eventing the expression of the structural genes. Direct repression of the structural genes is also existant. In the proline utilization path way, repression operates directly at the level of the structural genes . In the ethanol regulon, CreA prevents the self-induction of alcR and the induction of the structural genes by competing with the binding o f the AlcR protein. In proline gene cluster, CreA does not interfere w ith induction mediated by PrnA but with the activity of an unknown and more general transcription factor.