Hyper-repressible operator-type mutant in sulphate permease gene of Aspergillus nidulans

Abstract

SINCE the pioneering work on regulation of the lac operon in Escherichia coli¹ a great number of operator mutations have been described. In eukaryotic organisms, however, only a few mutations affecting cis-acting regulatory element (some of which can be formally interpreted as operator mutants) have been reported^2–6. The term ‘operator’ in the case of eukaryotes is used in an operational sense as it is not known whether it describes a molecular organisation similar to that found in bacteria. This report describes a mutant of Aspergillus nidulans altered at a site closely linked to the sB gene for sulphate permease⁷. This mutation causes a hypersensitivity of this gene to repression by sulphur amino acids.