Stem cell factor activates STAT-5 DNA binding in IL-3-derived bone marrow mast cells

The Kit tyrosine kinase regulates growth and differentiation of many hematopoietic cells through a signal transduction process that remains to be fully elucidated. Kit has been shown to associate with the receptor for erythropoietin (Epo), which is known to activate the signal transducer and activator of transcription, STAT-5. To determine if Kit signal transduction activated latent DNA-binding factors, including STAT-5, we performed electrophoretic mobility shift assays on stem cell factor (SCF)-stimulated mouse bone marrow-derived mast cells (BMMCs). SCF led to the rapid and transient activation of a DNA-binding factor that was identified by supershift analysis as STAT-5. STAT-5 DNA binding was shown to be specific for the oligonucleotide of the correct sequence and was dose-responsive. Epo stimulation of BMMCs led to the activation of a DNA-binding activity that comigrated with the SCF-induced band, but peaked and was maintained at later time points than SCF-induced activation. These data indicate that SCF stimulation of Kit leads to activation of STAT-5 DNA binding with kinetics distinct from Epo-mediated stimulation.