Fig. 5
Additional negative feedback suppresses p53 upregulation by enhancing the pulsing response of p53. A Pathway diagrams with Type 1- or Type 2-negative feedback in addition to the central p53-Mdm2 negative feedback. NF denotes the negative feedback gene that is a transcriptional target of p53. B Dose response of p53 dynamics under strong negative feedback strength (left panel: Type 1; right panel: Type 2). C Correlation of the different p53 dynamic phenotypes with the indicated negative feedback parameters. The negative feedback strength is determined mainly by γf (the degradation rate of NF) for the Type 1 motif (denoted in blue), and kf0 (the basal production rate of NF) and \({k}_{\mathrm{mf}}^{\mathrm{n}}\) (the rate constant of Mdm2-NF interaction) for the Type 2 motif (green). D Comparison of the expression levels of Wip1 in the five selected cancer cell lines after a 24-h treatment of the indicated Nutlin-3a or 5-FU concentrations. E p53 expression levels and the representative single-cell trajectories of p53 dynamics under Wip1 knockdown (siWip1) vs. control in MCF7 cells after a 24-h treatment of 10 μM Nutlin-3a and 50 μM 5-FU. F Single-cell statistics of MCF7 cells exhibiting sustained p53 induction under the indicated RNAi and drug treatment conditions. Data were averaged from 3 independent sets of single-cell imaging experiments. The total number of cells analyzed for each condition in each imaging experiment ranged from 52 to 169. Error bars indicate standard deviations (SDs). P value was obtained by Student’s t test comparing the results under Wip1 knockdown (siWip1) with siRNA control (siCtrl). *P < 0.005. The individual data from each imaging experiment are provided in the Additional file 2 and denoted by the open circles in the figure. G Pathway diagram of the ATM/p53/Mdm2/Wip1 regulatory module that mediates the cellular response to Etoposide. The phosphatase, Wip1, constitutes an additional, dual negative feedback of Type 1 plus Type 2. H The dose response of p53 dynamics in the absence of Wip1 (left panel) and in the presence of a weak Wip1-negative feedback (right panel). I Detailed features of the p53 pulsing dynamics depend on τwip1, the time delay in p53-induced Wip1 upregulation