FIG. 5.
The C/EBPδ APRE competes for binding of Stat3 to the α2-m APRE. (A) EMSA using the rat α2-m APRE, nuclear extracts (6.5 μg) from HepG2 cells, and NRS or Stat3-specific antibody (Ab) as indicated. The HepG2 cells were treated with IL-6 for 15 min. An upper complex (u) and a lower complex (l) appear in the IL-6-treated extracts (lane 3). The Stat3 antibody supershift complex (lane 4) is indicated. (B) Competition for Stat3 binding by the C/EBPδ APRE. Nuclear extracts (10 μg) from IL-6 treated HepG2 cells were incubated with Stat3-specific antibody and 10× (lanes 3 and 6), 30× (lanes 4 and 7), or 100× (lanes 5 and 8) molar excess of unlabeled wild-type (δAPRE) or mutant (δAPREm) binding site, as indicated. The rat α2-m APRE was used as a probe. The film was overexposed to emphasize the supershifted complex.