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 h ematopoietic cells through a signal transduction process that remains to be fully elucidated. Kit has been shown to associate with the recep tor for erythropoietin (Epo), which is known to activate the signal tr ansducer and activator of transcription, STAT-5. To determine if Kit s ignal transduction activated latent DNA-binding factors, including STA T-5, we performed electrophoretic mobility shift assays on stem cell f actor (SCF)-stimulated mouse bone marrow-derived mast cells (BMMCs). S CF led to the rapid and transient activation of a DNA-binding factor t hat was identified by supershift analysis as STAT-5. STAT-5 DNA bindin g was shown to be specific for the oligonucleotide of the correct sequ ence and was dose-responsive. Epo stimulation of BMMCs led to the acti vation of a DNA-binding activity that comigrated with the SCF-induced band, but peaked and was maintained at later time points than SCF-indu ced activation. These data indicate that SCF stimulation of Kit leads to activation of STAT-5 DNA binding with kinetics distinct from Epo-me diated stimulation.