U19 expression inhibits p53-dependent check-point arrest.

<p>(<b>A</b>) Cell cycle analyses of wt HCT116 cells, HCT116 cells stably expressing U19, and HCT116-p53^−/− cells. The cells were stained with NIM-DAPI and analyzed by flow cytometry. Four independent experiments are shown. (<b>B</b>) Quantification of the G1, S and G2 distributions, using the Dean-Jett-Fox algorithm in the Flow-Jo software program. An average of the four independent experiments from (A) is shown. Error bars indicate SD. The p values in G1 are: 1) p = 0.0005; 2) p = 0.0003; and 3) p = 0.49 (p values were determined using a t-test). (<b>C</b>) Analysis of p21 promoter activation using a p21-pro-<i>luciferase</i> construct. HCT116 wt cells and HCT116 cells stably expressing U19 were transfected with a p21-Luc promoter construct, γ-irradiated (30 Gy followed by 24 hrs of incubation) and analyzed for luciferase induction. Y-axis depicts relative light units (RLU). A representative out of two experiments is shown. Values are average of triplicate measurements with error bars indicating SD. (<b>D</b>) Real-time PCR on mRNA from HCT116 wt, U19S and p53^−/− cells with <i>MDM2</i> or <i>TBP</i> specific primers. <i>MDM2</i> mRNA levels are represented relative to <i>TBP</i>. Measurements were performed in duplicate. Two independent experiments is shown.