Figure 3

Analysis of growth rates and cell cycle distribution in Topors^+/+ and Topors^-/- pMEFs. A. Expression of Topors RNA and protein in early passage pMEFs. Lysates were obtained from pMEF cell lines of the indicated genotype. As indicated, RNA expression was evaluated by RT-PCR, using primers spanning Topors exons 2-3, or within exon 3 alone. Actin RNA expression was evaluated using β-actin-specific primers. The right panel shows Topors protein expression evaluated by immunoblotting nuclear lysates with a polyclonal antibody generated against the human protein. Tubulin immunoblotting is shown as a control for relative protein content. B. Cellular proliferation was assayed in triplicate in Topors^+/+ (solid line with circles) and Topors^-/- (dotted line with squares) early passage pMEFs. C. Representative cell cycle distributions as determined using propidium iodide staining and flow cytometry. The table lists mean and standard deviations of cell cycle distribution data obtained from two independent pMEF cell lines. Statistical analyses indicated no significant differences in mean values of cell cycle phases.