Figure 6.

Introduction of pnp gene rescue response to H₂O₂ insult. (A) pKAK7 harboring the pnp gene (23) and the control plasmid pBR322 were introduced into the wild-type and pnp mutant cells, respectively. Midlog cultures containing 50 μg/mL ampicillin were serially diluted and inoculated on YT agar plates with or without 0.5 mM H₂O₂ to determine H₂O₂ sensitivity. (B) Total RNA was isolated 15 min after treatment with or without 0.5 mM H₂O₂, and the level of 8-oxoG in RNA was determined by HPLC. The mean of duplicate experiments and standard errors are shown. (C) Cultures at OD_550nm = 0.5 (0 min) were treated for 1 h with or without 1 mM H₂O₂. PNPase activity was measured by ADP incorporation into RNA using 6 μg of protein in each 50 μL reaction. The averages of two measurements and standard errors are shown.