Co(III)-Ci prevents target gene activation by a full length, constitutively active Ci. S2R+ cells were transfected with a constitutively active form of Ci, Ci(m1-4) (all columns), either the Ci responsive ptcΔ136-Fluc luciferase vector (columns 2–8) or ptcΔ136mut-Fluc in which the Ci binding sites have been mutated (column 1), and 150ng of either Ci binding site oligos (column 3), Co(III)-Ebox (column 4), Co(III)-CiMut (column 5), Co(III)-Ci (column 6) or 75 ng of Co(III)-CiMut (column 7) or Co(III)-Ci (column 8). Cells were then incubated for 12 hours, lysed and assayed for luciferase activity. Experiments were performed in triplicate and error bars represent one standard deviation.