Figure 1.

Gene activation by various nonclassical activators in yeast. (A) Transcriptional activation elicited by Pho4 derivatives at the PHO5 gene. All the Pho4 fusions were expressed from the PHO4 promoter on a high-copy (2 μ) vector (24). Activity was measured as acid phosphatase units produced by the product of the PHO5 gene directly off its chromosomal locus under high phosphate conditions in a pho80 strain (YAG23). Wild-type Pho4 was carried on an ARS-CEN plasmid because overexpression of Pho4 causes severe growth defects (24). (B) Transcriptional activation elicited by LexA derivatives at an HIS3-based reporter template. All the LexA fusions were expressed from the ADH1 promoter on a high-copy (2 μ) vector. Transcriptional activity was measured as β-galactosidase units produced by the lacZ gene product in yeast strain FT4a. The reporter construct was carried on a 2 μ plasmid.