FIG. 4.

Antisera to ATF1, but not ATF2, specifically affect the c-Jun ATF complexes. (A) Gel mobility shift assays were performed with the c-jun ATF site probe and in vitro-translated ATF1 (lanes 1 to 4), in vitro-translated ATF2 (lanes 5 to 8), mock in vitro translation extract (lane 9), or HeLa cell nuclear extracts (lanes 10 to 13). Either no serum (−), nonimmune serum (NRS), or anti-ATF1 or anti-ATF2 serum was added as indicated. (B) HeLa nuclear extracts were assayed with an AP1 consensus site probe and the indicated sera. Arrows D and C mark complexes obtained with in vitro-translated ATF1 and ATF2. Antibody-supershifted complexes are marked with arrows A and B. Complex E shows the complex binding to the consensus AP1 site. The arrowheads to the right indicate a nonspecific complex obtained with nonimmune serum.