FIGURE 1: Growth phenotypes of S. cerevisiae cells. (A) Structure of the CUP1 locus on the genome of WT and cup1Δ strain. The DNA region from 1,533 bp upstream of CUP1-1 coding region to 338 bp downstream of CUP1-2 coding region was substituted with natNT2 transformation cassette to construct the cup1Δ strain. (B) The CUP1 mRNA was determined by RT-qPCR in each strain. The relative mRNA level was calculated with WT with an empty vector as 1.0 using ACT1 gene as a reference. The values are the means and standard deviations from at least three independent experiments. Statistic significances of differences were analyzed by Student's t-test (*p < 0.05). (C) Spot assay of S. cerevisiae under stress conditions. Each strain was cultured until the exponential phase in SD liquid medium (pH 6.0) at 25°C, and the serial dilutions were spotted onto SD medium (pH 4.6) with or without of 1.4 mM NaNO_2, or 20 μM CuSO₄ followed by incubation at 30°C for the indicated time. (B, C) The appropriate strains harboring an empty vector (+ vector), or overexpresses CUP1 (+ CUP1-OE) or CUP1his (+ CUP1his-OE), were used.