JAK2 IS REQUIRED FOR INDUCTION OF THE MURINE DUB-1 GENE

Cytokine receptors activate multiple signal transduction pathways, res ulting in the induction of specific target genes. We have recently ide ntified a hematopoietic cell-specific immediate-early gene, DUE-I, tha t encodes a growth-regulatory deubiquitinating enzyme. The DUE-I gene contains: a 112-bp enhancer element that is specifically induced by th e beta c subunit of the interleukin-3 (IL-3) receptor. To investigate the mechanism of DUE-I induction, we examined the effects of dominant- negative forms of JAK kinases, STAT transcription factors, and Raf-l i n transient transfection assays. In Ba/F3 cells, IL-3 induced a dose-d ependent activation of DUB-I-luciferase (luc) and GAS-luc reporter con structs. A dominant-negative form of JAK2 (truncated at amino acid 829 ) inhibited the induction of DUB-1-luc and GAS-luc by IL-3. A dominant -negative form of STAT5 (truncated at amino acid 650) inhibited the in duction of GAS-luc but not DUB-1-luc. A dominant-negative form of Raf- l inhibited the induction of DUB-1-luc but had no effect on the induct ion of GAS-luc by IL-3. The requirement for JAK2 in the stimulation of the DUE-I enhancer was further supported by the suppression of DUB-1 induction in Ba/F3 cells stably expressing the dominant-negative JAK2 polypeptide. We hypothesize that IL-3 activates a JAK2/Raf-1 signaling pathway that is required for DUE-I induction and is independent of ST AT5.