Figure 5.

An overexpression screen of yeast peroxidases reveals that only Tsa1 and Tsa2 protect against H₂O₂ and suppress mutations in tsa1Δ tsa2Δ yeast. (A) Western blot analysis of FLAG-tagged peroxidases. Pgk1 levels were monitored as a loading control. (B) Stationary phase cultures of wild-type (BY4741) cells transformed with vector, tsa1Δ tsa2Δ cells transformed with vector, or tsa1Δ tsa2Δ cells expressing FLAG-tagged peroxidases were diluted serially, plated on non-selective growth medium (YPD) or YPD containing 4 mM H₂O₂, and grown for 48 h at 30 °C. Results are representative of three independent experiments. (C) Mutation rates in cells expressing various peroxidases were determined by monitoring fluctuation of the CAN1 gene, as assessed by counting canavanine-resistant colonies for nine independent isolates of each strain in duplicate. The graph depicts the median mutation rate ± the 95% confidence limit for each strain. Detailed methods are available in Supplementary Materials.