Fig. 8. Effect of dynamin on ribonuclease-mediated cytotoxicity. (A) K44A Dyn cells grown for 2 days in the presence (induced) or absence (uninduced) of tetracycline were fixed and stained with TRITC-conjugated phalloidin to detect actin filaments (red). The production of wild-type dynamin and its K44A variant was monitored by immunoblotting using anti-HA antibodies. (B) The toxicity of G88R RNase A and ONC was measured for cells overproducing wild-type dynamin or K44A dynamin. Cells were grown in the absence of tetracycline for 2 days to induce overproduction. Then, increasing concentrations of G88R RNase A and ONC were added. After a 48 hour incubation at 37°C, DNA synthesis was measured as described in Materials and Methods. As a control, the effects of G88R RNase A and ONC were measured on cells not overproducing either form of dynamin. Each point represents the percent of [methyl-³H]thymidine incorporated compared to a PBS control and is the mean (±s.e.) of at least three separate experiments with triplicate samples.