Regulation of pyrimidine salvage in Aspergillus nidulans: a role for the major regulatory gene are A mediating nitrogen metabolite repression.

The synthesis of thymine 7-hydroxylase, an alpha-ketoglutarate dependent dioxygenase, is subject both to nitrogen metabolite repression and to oxygen repression, while synthesis of the other pyrimidine salvage pathway dioxygenase, pyrimidine deoxyribonucleoside 2'-hydroxylase, is subject to neither. are A300, an allele of the positive acting regulatory gene are A mediating nitrogen metabolite repression in Aspergillus nidulans, considerably elevates levels of thymine 7-hydroxylase, probably alleviating at least partly both nitrogen metabolite repression and oxygen repression. are A300 has little or no effect on levels of pyrimidine deoxy-ribonucleoside 2'-hydroxylase but does elevate net uptake capacities for thymine, thymidine and deoxyuridine two-fold. are A300 was selected as allowing thymine to supplement a pyrimidine auxotrophy and was found to allow supplementation by thymidine, other pyrimidine nucleosides and pyrimidine salvage intermediates as well. This is the first reported evidence for are A control over an activity(-ies) not directly concerned with nitrogen source utilization.