The effect of the v-abl oncogene of the Abelson murine leukemia virus (A-MuLV) on the Jak-STAT pathway of cytokine signal transduction was investigated. In murine pre-B lymphocytes transformed with A-MuLV, the Janus kinases (Jaks) Jaki and Jak3 exhibited constitutive tyrosine kinase activity, and the STAT proteins (signal transducers and activators of transcription) normally activated by interleukin-4 and interleukin-7 were tyrosine- phosphorylated in the absence of these cytokines. Coimmunoprecipitation experiments revealed that in these cells v-Abl was physically associated with Jaki and Jak3. Inactivation of v-Abl tyrosine kinase in a pre-B cell line transformed with a temperaturesensitive mutant of v-abl resulted in abrogation of constitutive Jak-STAT signaling. A direct link may exist between transformation by v-abl and cytokine signal transduction.
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