STF IL-4 - A NOVEL IL-4-INDUCED SIGNAL-TRANSDUCING FACTOR

The mechanism by which interleukin-4 (IL-4) regulates the expression o f particular genes is unknown. We have determined that IL-4 induces a DNA binding factor (termed STF-IL-4) which has a strong affinity for a n IFN-gamma activation site (GAS). Interestingly, STF-IL-4 also binds to the IL-4 responsive promoter for the Ig heavy chain germline epsilo n transcript. The IL-4 dependent activation of STF-IL-4 is rapid, does not require protein synthesis and results in the sequential appearanc e of binding activity first in the cytoplasm and then later in the nuc leus. Activation of STF-IL-4 is sensitive to tyrosine kinase inhibitor s and the active factor is tyrosine phosphorylated. This pattern of ac tivation is similar to the activation of interferon-induced transcript ion factors. STF-IL-4 appears to be a new member of a growing family o f cytokine-induced transcriptional regulators.