FIGURE 4.

A novel method to measure promoter strength applied to the study of arginine-regulated genes. A, the promoter of the gene of interest was fused to the HSV1-TK and expressed in a high copy plasmid. FIAU is phosphorylated by HSV1-TK and becomes a toxic compound once incorporated into DNA, reducing the growth rate. The table indicates the expected influence of FIAU on the growth rate of cells transformed with HSV1-TK fused to an active or inactive promoter. The rate of growth inhibition is proportional to the strength of the promoter studied. Yeast strains expressing HSV1-TK gene under the control of either ADH1 (B) or GAL1 (C) promoters are shown. ADH1 is active in the presence of glucose. GAL1 promoter is down-regulated in the presence of glucose and strongly up-regulated when galactose is the sole carbon source. Growth profiles in minimal medium containing ammonium as unique nitrogen source are shown. Error bars correspond to S.E.