Figure 3.

Blocking apoptosis does not alter cell-cycle arrest after Hoxb8 withdrawal. (a) Bax^−/−;Bak^−/− Hoxb8 FDM cells arrest in G1 after Hoxb8 downregulation. Bax^−/−;Bak^−/− Hoxb8 FDM cells were cultured in the presence of IL-3 and absence of 4-OHT and, at the indicated times were subjected to cell-cycle analysis using hypotonic PI staining. Results were analysed using Modfit and show means±S.E.M. of five independent clones in two independent experiments. (b) Bim^−/− Hoxb8 FDM cells undergo cell-cycle arrest after Hoxb8 downregulation. Wild-type and Bim^−/− Hoxb8 FDM cells were cultured for the indicated times without 4-OHT and then subjected to cell-cycle analysis using hypotonic PI staining. The inset shows representative histograms of hypotonic PI staining 3 days after 4-OHT withdrawal of wild-type and Bim^−/− Hoxb8 FDM cells. Results were analysed using Modfit and show means±S.E.M. of eight independent clones in three independent experiments. (c) Clonogenicity declines after Hoxb8 downregulation. Wild-type, Bim^−/− and Bax^−/−;Bak^−/− Hoxb8 FDM cells were cultured for the indicated times without 4-OHT before being plated in soft agar in the presence of 4-OHT. Colonies were counted after 14 days and relative clonogenicity determined. Results shown are means±S.E.M. of four independent clones of each genotype in three independent experiments