Supershift experiments at TH–AP-1 site, using Fos/Jun family antibodies after the treatment of E14 striatal neurons with aFGF alone or individual coactivators. A, Autoradiogram showing the results of a supershift experiment with E14 striatal neurons fed DM (Control) or DM containing 10 ng/ml aFGF. The stimulation of striatal neurons by aFGF resulted in the appearance of two new supershifted c-Fos bands (lane 10a,b) and increased binding of Fos-B (lane 11) and Jun-D (lane 16) at the TH–AP-1 site; c-Jun (lane 14) remained the same intensity as compared with the control. Experiments were conducted as described in the Figure 4A legend. B, Autoradiogram showing the results of a supershift experiment with striatal neurons fed DM (Control) or DM containing 20 μm DA. Only the supershifted complex containing Jun-D (lane 16) increased binding to the AP-1 site in contrast to the control (lane 8). The binding of Fos-B (lane 11) and c-Jun (lane 14) was the same as for control (lanes 3, 6). No c-Fos was detected in either control (lane 2) or DA-stimulated striatal neurons (lane 10).C, Autoradiogram showing the results of a supershift experiment with striatal neurons fed DM (Control) or DM containing 0.25 mm IBMX and 50 μmforskolin. After stimulation the binding of Fos-B and Jun-D to the TH–AP-1 site increased as compared with control (lanes 3, 8, 11, 16), whereas c-Jun remained the same as control (lanes 6, 14). c-Fos, Fra-1, Fra-2, and Jun-B were not detected in both stimulated (lanes 10, 12, 13) and control neurons (lanes 2, 4, 5). Note that the IBMX/forskolin treatment produced a preponderance of proteins in the high-affinity upper AP-1 complex. D, Autoradiogram showing the results of a supershift experiment with striatal neurons fed DM (Control) or DM containing 200 nm TPA. The amount of Fos-B and Jun-D binding at the TH–AP-1 site was lower in the striatal neurons stimulated with TPA (lanes 11, 16) than in the control neurons (lanes 3, 8); c-Jun remained the same as control neurons (lanes 6, 14). Supershift complexes of c-Fos, Fra-1, Fra-2, and Jun-B were not detected in either control (lanes 2, 4, 5) or stimulated neurons (lanes 10, 12, 13).