Ligand-specific Notch1 and Notch2 binding and signal strength transmission. (A) Staining of control-Fc, Notch1-Fc, and Notch2-Fc fusion proteins to K562 cells expressing the different Notch ligands as indicated. (B) Ligand-specific representation of the same data as in panel A. (C) Luciferase reporter assay of U2OS Tet-on flp-in-Notch1 and U2OS Tet-on flp-in-Notch2 cells cotransfected with CBF-luciferase reporter plasmid pGL2-Gal4-luciferase and the normalizing plasmid pRL-TK-expressing Renilla luciferase. After plasmid transfection, cells were cocultured with K562 expressing DLL1, DLL4, JAG1, JAG2, or control for 24 hours, and thereafter luciferase activity was measured. Bar graphs represent the average of 3 independent experiments. Errors bars represent SEM.