Identification of the components of E2F complexes in human proliferating primary CD34⁺ cells by supershift assays. CD34⁺ cells were purified and were induced to proliferate by the addition of cytokines as described in Materials and Methods. After 4 days, whole cell extracts were prepared and EMSA and supershift assays were performed as described in Fig 3. Three complexes (C, D, and E) were detected. Specific supershifted complexes were observed on addition of anti-E2F–4 antibody (lane 5) and anti-DP–1 antibody with control peptide (lane 6), but not with DP-1 peptide (lane 7). The upper complex (C) shifts with anti-p107 antibody (lane 8) and a shift was also seen with anti-p130 antibody (lane 9). An anti-E2F–1 antibody had no effect (lane 4). Proliferating T cells were run as a control (lane 1) and show a supershift with anti-E2F–1 antibody (lane 2, arrowed). The data are representative of four experiments with individual CD34⁺ cell isolates.