Subcellular localization of EGR-1 and Sp1 in HUVEC. Immunofluorescence staining of EGR-1 in unstimulated endothelial cells (C) and cells stimulated with VEGF for 15 minutes (D), 1 hour (E), 6 hours (F), and 8 hours (G). Preabsorbtion of the anti–EGR-1 antibodies with an appropriate peptide abolished both cytoplasmic and nuclear staining of unstimulated (A) and VEGF-stimulated cells (B). Sp1 staining was exclusively nuclear and identical for all time points (H through L). The picture is representative of four experiments with similar results.