THE ASPERGILLUS-NIDULANS YA GENE IS REGULATED BY ABAA

The developmentally regulated Aspergillus nidulans yA gene encodes a p -diphenol oxidase that is needed for synthesis of green conidial pigme nt. We subjected the yA 5' flanking region to mutational analysis in A .nidulans and Saccharomyces cerevisiae to identify DNA sequence elemen ts involved in its transcriptional control, and identified two functio nally distinct elements. Element I contained potential BrlA binding si tes and was required for full level yA transcription, but not for deve lopmental regulation in the presence of element II. Element II contain ed putative TEF-1 binding sites flanking a CCAAT element and was suffi cient for developmental regulation of transcription. Mutation of the T EF-1 binding sites eliminated developmental regulation, whereas mutati on of the CCAAT element led to elevated levels of transcription. Eleme nt II was also sufficient to induce transcription in S. cerevisiae whe n the A. nidulans developmental regulatory gene abaA was expressed fro m the GAL1 promoter. As AbaA and TEF-1 possess similar DNA binding dom ains, the abaA-yA interaction in yeast is probably direct. Thus, abaA appears to be a direct activator of yA, but yA regulation may also inv olve interactions with BrlA and a member of the CCAAT class of DNA bin ding proteins.