Fig. 4. Overexpression of Bir1p prevents apoptosis-like cell death. Confocal fluorescence (first, third and fifth column of panels), and coincident fluorescence and differential-interference-contrast (second, fourth and sixth column of panels) images are shown. (A) Wild-type cells (BYa), cells overexpressing Bir1p and cells simultaneously overexpressing Bir1p and Nma111p were treated with 0.8 mM H₂O₂ for 4 hours to induce apoptosis. DNA was visualized by Sytox-Green nucleic acid stain. DNA-strand breaks were detected by the TUNEL test and ROS by DHR staining. Bars, 2.5 µm (DNA), 5 µm (ROS); 10 µm (TUNEL). (B) Survival rates of yeast cells overproducing Bir1p compared with overproducers of Bir1p/Nma111p or Nma111p, without pre-treatment or after incubation with 0.4 mM H₂O₂ for 24 hours. Error bars, mean + s.e.m.