FIGURE 1.

Reversible cell cycle arrest. HT29 (A) and HT29-tsp53 cells (B) were incubated for 16 h at either 32°C or 38°C, as indicated. Cells incubated at 32°C were then either returned to 38°C or maintained at 32°C for up to 24 h, as indicated. Thirty minutes before collection, BrdU was added to the culture medium to label nascent DNA. Cells were then subjected to two parameter flow cytometric analysis. The early S-phase population in B is indicated by the box. (C) Quantitative analysis of independent experiments like those presented in panel B. Each value represents the mean (±SEM) determined from three independent experiments. (D) HT29 and HT29-tsp53 cells were incubated for 16 h at 32°C and were then returned to 38°C for the indicated time in hours (T). Cell lysates were collected for immunoblot analysis. The control sample (designated C) was collected from cells maintained at the restrictive temperature.