FIG. 7.

Model for regulation of the ADE regulon by Bas1 and Pho2. The binding of Bas1 and Pho2 at the ADE5,7 promoter is depicted under repressing and derepressing conditions. The DNA binding domains of Bas1 and Pho2 are shown as a solid black oval and circle, respectively, marked with a “1” for Bas1 and a “2” for Pho2. The activation domains for both proteins are shown as hatched squares under repressing conditions (+ade) and as solid diamonds under derepressing conditions (−ade). The mutual interaction domains are shown as hatched rectangles. The basal and derepressed levels of transcription under the two conditions are indicated by narrow and broad arrows, respectively.