Down-regulation of Bcl-x_L and c-myc by expression of dominant- negative STAT3 in MO7e cells bearing D816H mutant c-Kit.

(A) Cytosolic extracts from representative clones in each experimental group were incubated with ³²P-labeled SIEm67 probe, followed by EMSA. (B) Total cellular lysates were analyzed by Western blotting (WB). In the left panel, the upper part was the blot probed with anti–Bcl-x_L antibody. Blot from the upper part was stripped and reprobed with antitubulin antibody to verify the protein loading, as shown in the lower part. Density of the bands was determined by densitometry analysis and the Bcl-x_L–tubulin ratios are shown in the right panel. (C) Total RNA was analyzed by Northern blotting (NB). In the left panel, the upper part was the blot hybridized with a c-myc–specific probe. Blot from the upper part was stripped and rehybridized with GAPDH-specific probe to verify RNA loading, as shown in the lower part. Density of the bands was determined by densitometry analysis and the c-myc/GAPDH ratios are shown in the right panel. These analyses were performed on 3 different clones transfected with each of the STAT (St) cDNAs or vector alone. Within each group of transfectants, similar patterns of EMSA binding as well as Bcl-x_L and c-myc expression were observed. Results of representative clones are depicted.