Requirement of upstream activation sequences for nitrogen catabolite repression of the allantoin system genes in Saccharomyces cerevisiae.

Synthesis of the transport systems and enzymes mediating uptake and catabolism of nitrogenous compounds is sensitive to nitrogen catabolite repression. In spite of the widespread occurrence of the control process, little is known about its mechanism. We have previously demonstrated that growth of cells on repressive nitrogen sources results in a dramatic decrease in the steady-state levels of mRNA encoded by the allantoin and arginine catabolic pathway genes and of the transport systems associated with allantoin metabolism. The present study identified the upstream activation sequences in the 5'-flanking regions of the allantoin system genes as the cis-acting sites through which nitrogen catabolite repression is exerted.