A1 induction is intact in NF-κB–deficient mast cells. (A,B) Reverse transcriptase PCR (RT-PCR) analysis of A1 expression in BMMCs deficient for 3 NF-κB subunits c-Rel (c-rel^−/−) or c-Rel plus NF-κB1 p50 (c-rel^−/−nfκb1^−/−) (A) or RelA (rela^−/−) (B) shows strong induction of A1 after IgER CL or ionomycin stimulation. (C) IgER CL increases A1 mRNA levels in C57 cells stably transfected with the nondegradable NF-κB super-repressor, IκB-α SR. Western blot analysis (WB) of cytosolic and nuclear extracts reveal intact IκB levels after IgER CL and an active IκB-α SR. The IκB-α SR is of human origin and runs at a slower mobility. (D) EMSA shows less protein-DNA complex of nuclear RelA and the oligonucleotide probe containing an RelA binding site, from C57 stable transfected with an active IκB-α SR compared with C57 cell transfected with an empty vector. Probing for GAPDH and ERK was used as loading controls in RT-PCR and Western blot analyses, respectively. RT-PCR experiments in panels A, B, and C were performed 3 times with similar results, whereas the Western blots and EMSA in panels C and D were performed twice and once, respectively.