Characterization of the interleukin-4 nuclear activated factor/ STAT and its activation independent of the insulin receptor substrate proteins.
The activation of a latent DNA binding factor by interleukin-4 ( IL-4), the IL-4 nuclear activated factor ( IL-4 NAF), occurs within minutes of IL-4 binding to its receptor. Molecular characterization of IL-4NAF by ultraviolet light cross-linking experiments revealed a single protein of 120-130 kDa in contact with the DNA target site. Glycerol gradient sedimentation analysis indicated a molecular mass of IL-4 NAF consistent with a monomer that is capable of binding DNA. The IL-4 NAF target site is a palindromic sequence that is also recognized by the interferon-induced transcription factor, p91/STAT1 alpha. However, IL-4 NAF and p91/STAT1 alpha display distinguishable DNA binding specificities that may generate one level of specificity in the expression of target genes. Previous studies suggested the involvement of the insulin receptor substrate-1 ( IRS-1) in the IL-4 signal transduction pathway. Although IRS-1 is involved in the stimulation of mitogenesis, our results demonstrate that activation of IL-4 NAF is independent of IRS-signaling proteins. The results of this study indicate that IL-4 stimulates bifurcating signal pathways that can direct mitogenesis via the IRS-signaling proteins and specific gene expression via the IL-4 NAF.[1]References
- Characterization of the interleukin-4 nuclear activated factor/STAT and its activation independent of the insulin receptor substrate proteins. Kotanides, H., Moczygemba, M., White, M.F., Reich, N.C. J. Biol. Chem. (1995) [Pubmed]
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