Bcl-3 is associated with NF-κB p52 in TF-1 cells (EMSA). (A) Six micrograms of nuclear extracts prepared from TF-1 cells stimulated with GM-CSF for 24 hours was incubated with different NF-κB antibodies for 10 minutes before adding a³²P-labeled c-myb κB binding oligonuclear probe. Three DNA-protein complexes were generated. Complexes 2 and 3 (C2 and C3) were supershifted by anti-p50; C1, C2, and C3 were shifted by anti-p52. C1 was reproducibly inhibited by anti–Bcl-3 antibody (with a long exposure, a supershifted band was also visible). However, anti-RelB and anti–c-Rel had no effect on any of these complexes. Similar results were observed in 3 experiments. (B) EMSA was performed with growth factor-deprived TF-1 cells or TF-1 cells induced with GM-CSF for 24 hours. The C1 complex was greatly increased by GM-CSF stimulation, whereas other complexes had no significant change. This experiment was repeated 3 times with similar results.