Tyrosine phosphorylation and DNA binding of STAT1 and STAT3 induced by G-CSF is not affected by SCF.

MO7e-G cells were factor starved overnight, then treated for 15 minutes with SCF (100 ng/mL), G-CSF (1 or 100 ng/mL), or both. (A) Total cell extracts were prepared and Western blots were performed to detect total and tyrosine-phosphorylated forms of STAT1 and STAT3. The same membrane was stripped and reprobed for each blot. (B) Nuclear extracts were prepared and binding was assessed to a ³²P-labeled double-stranded oligonucleotide containing a STAT-binding high-affinity sequence. G-CSF was used at a concentration of 1 ng/mL. Ia, Ib, and Ic indicate specific STAT-DNA complexes; II, “super-shifted” complexes; III, nonspecific complexes.