Figure 6

Activation of p53 in response to repeated damage induction. (A) Schematic representation of the experimental design. Cells were damaged with a low dose of NCS and analyzed for the activation of a p53 pulse. The same cells were re-damaged with the same dose of NCS 6hr after the first damage treatment. (B) Schematic representation of p53’s first pulse (pulse I; light blue) and second pulse (pulse II; dark blue). Note that since the duration of each p53 pulse is about five to six hours, the second NCS treatment was applied after the first pulse has been completed. (C) The fraction of cells showing pulse I (light blue) or pulse II (dark blue) in response to one NCS treatment (single stimulus) or two subsequent NCS treatments (double stimulus) at the indicated concentrations. The second treatment of NCS did not lead to a higher fraction of cells with pulse II. (D) The number of 53BP1 foci was quantified before and at the indicated time points after treatment with low doses of NCS (50 and 25 ng/ml). Red lines indicate the median. (E) The fraction of cells showing a p53 pulse in response to the second damage treatment is shown for two different NCS concentrations (light blue bars = cells that induced a p53 upon the first treatment, dark blue bars = cells that did not respond after the first stimulus). Error bars represent the standard error of the proportion. Number of cells = approximately 700. NCS, neocarcinostatin.