Skip to main content
. 1997 Feb 4;94(3):820–825. doi: 10.1073/pnas.94.3.820

Figure 4.

Figure 4

Effects of yDr1 overexpression in vivo. (A and B) mRNA levels decline by overexpression of yDr1 and Bur6. RNA samples were prepared from galactose-induced (Gal) or uninduced (Glu) cultures of the indicated yeast strains, which contain either the YDR1 and BUR6 genes (Dr·B6) or vector controls. Each lane corresponds to the time points (in hours) at which aliquots of cells were taken from the culture following galactose induction. (A) Amounts of Pol II, Pol III, and Pol I transcript were determined by probing RNA samples obtained at various time points with labeled oligo(dT) (lanes 1–4), tRNAW (lanes 5–8), or rRNA (lanes 9–12). Row 1, uninduced culture of the control strain containing vectors only; row 2, induced culture of the strain containing vectors only; row 3, uninduced culture of the strain containing YDR1 and BUR6 constructs; row 4, induced culture of strain containing YDR1 and BUR6 constructs. Under these conditions Dr1 was overexpressed ≈5-fold with respect to the wild-type strain, as determine using quantitative Western blots. (B) Equivalent amounts of RNA were hybridized with 32P-labeled oligonucleotide complementary to ACT1 mRNA. After digestion with S1 nuclease, samples were subjected to denaturing PAGE. Lanes: 1–5, RNA samples from induced culture of the strain containing YDR1 and BUR6 constructs; 6–10, RNA samples from induced culture of the strain containing vectors only. (C) Toxicity of YDR1 overexpression is rescued by overexpression of SPT15 (TBP). Elevated expression of YDR1 from the GAL promoter in the presence of galactose as the sole carbon source impaired cell growth (vector, GAL/YDR1). This effect was rescued, resulting in near normal growth, by elevated expression of SPT15 from the GAL promoter (GAL/YDR1, GAL/SPT15). There is no growth phenotype associated with the presence of either vectors (vector, vector) or SPT15 alone (vector, GAL/SPT15) under inducing conditions. We wish to note that the toxicity associated with YDR1 overexpression was variable, ranging from minor effects on cell growth to nearly complete inhibition.