FIGURE 5.
E2f1–3 are important for cellular proliferation. The E2f3f/f-CSF-1R and E2f1−/−2−/−3f/f-CSF-1R cell lines were infected with either control- or cre- expressing retroviruses and then used for the following assays. A, BrdU incorporation in E2f3f/f-CSF-1R cell line. Quiescent MEFs with the indicated genotypes were restimulated with medium containing serum or CSF-1 and assessed for BrdU incorporation at the indicated time points. A total of 500 DAPI-stained nuclei from each cell line were counted, and the percentage of BrdU-positive cells is shown. B, E2f3f/f-CSF-1R MEFs were plated for a colony formation assay. Values shown have been corrected for deletion of E2f3 by colony PCR. C, BrdU incorporation of E2f1−/−2−/−3f/f-CSF-1R cell line. The graph shows the percentage of cells positive for BrdU incorporation. D, E2f1−/−2−/−3f/f-CSF-1R MEFs were plated for a colony formation assay. Values shown have been corrected for deletion of E2f3 by colony PCR. E, E2f3 PCR genotyping on genomic DNA from the cre-infected E2f3f/f-CSF1R and E2f1−/−2−/−3f/f-CSF-1R colonies grown in the presence of CSF-1. F, bar graphs showing -fold change in c-Myc expression in control and cre-treated E2f1−/−2−/−3f/f-CSF-1R after stimulation with serum (left) or CSF-1 (right).