Figure 2.

FL preferentially activates Stat5a in Baf3/Flt3 cells. (A) Growth factor–starved Baf3/Flt3 cells were stimulated with FL for 5 min. Stat5a and Stat5b were immunoprecipitated from cell lysates and immunoblotted with anti-phosphotyrosine antibody (pY). The same membrane was stripped and reblotted with anti-Stat5 antibody that recognizes both forms of Stat5. Results shown are from one representative of three experiments. (B) FL activates Stat5a DNA binding activity. Growth factor–starved Baf3/Flt3 cells were either untreated (control) or stimulated with FL for 10 min. Nuclear extracts from these cells were incubated with ³²P-labeled probe and subjected to EMSA. Oligonucleotide competition was performed by preincubating nuclear extracts with the cold probe. For supershifts, nuclear extracts were preincubated with the indicated anti-Stat5a or anti-Stat5b antibodies. The arrow indicates the DNA/Stat5 complex. Results shown are from one representative of two experiments.