Figure 1.
Flow cytometric analysis of immortalized wild-type (A), PARP−/− (B), and PARP−/−(+PARP) (C) fibroblasts. Cells were harvested 5 h after release from aphidicolin-induced G1-S block (Left) or 18 h after release from serum deprivation (Right). Nuclei then were prepared and stained with propidium iodide for flow cytometric analysis. In addition to the two major peaks of nuclei at G0-G1 and G2-M apparent in the DNA histograms of wild-type and PARP−/−(+PARP) cells, the DNA histograms of PARP−/− cells exhibit a third peak corresponding to the G2-M peak of an unstable tetraploid cell population (arrows).