NUCLEOTIDE-SEQUENCE, MESSENGER-RNA STABILITY, AND DNA RECOGNITION ELEMENTS OF CYS-14, THE STRUCTURAL GENE FOR SULFATE PERMEASE-II IN NEUROSPORA-CRASSA

The complete nucleotide sequence of the cys-14 gene which encodes sulfate permease II, a member of the sulfur regulatory circuit, is presented. The cys-14 gene contains four introns with consensus splice site sequences and is transcribed from four closely spaced initiation sites located approximately 20 bp upstream of the ATG initiation condon. The translated CYS14 protein is composed of 781 amino acids with a molecular weight of 87 037 and contains 12 potential hydrophobic membrane-spanning domains. cys-4 mRNA was found to turn over with a half-life of approximately 15 min, which presumably contributes to the regulation of sulfate permease II function. The cys-14 gene is highly expressed, but only in cells subject to sulfur limitation, and is turned on by the positive-acting CYS3 sulfur regulatory protein. Results are presented which show that CYS3 protein binds with higher affinity to DNA fragments which contain two or three tandem copies of a binding site sequence. Analyses of binding site specificity via mutated binding site elements showed that different regions of the partially symmetrical CYS3 binding site are important for recognition by the CYS3 regulatory protein.