Figure 4.

Effects of paromomycin in a upf3-Δ strain. (A) A upf3-Δ strains shows increased sensitivity to paromomycin. Sensitivity to this drug was determined in isogenic wild-type and upf3-Δ strains. Cells were plated in yeast extract/peptone/dextrose (YPD) medium and a disc containing 1 mg of paromomycin was placed on the lawn of cells. The diameter of the zone of growth inhibition was determined after the plates were incubated at 30°C for 2 days. (B) Isogenic wild-type and upf3-Δ strains were transformed with either −1 frameshift tester or 0-frame control plasmids. Increasing concentrations of paromomycin were added to cells inoculated at 0.1 OD₆₀₀/ml and grown at 30°C for 4 h. The efficiency of −1 ribosomal frameshifting was calculated by determining the ratio of β-gal activities measured on cells harboring the −1 frameshift reporter plasmid to those harboring the 0-frame control plasmid, grown under the same concentration of paromomycin, and multiplying by 100%.