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  • Title: Interferon regulatory factor 1 (IRF-1) and IRF-2 distinctively up-regulate gene expression and production of interleukin-7 in human intestinal epithelial cells.
    Author: Oshima S, Nakamura T, Namiki S, Okada E, Tsuchiya K, Okamoto R, Yamazaki M, Yokota T, Aida M, Yamaguchi Y, Kanai T, Handa H, Watanabe M.
    Journal: Mol Cell Biol; 2004 Jul; 24(14):6298-310. PubMed ID: 15226432.
    Abstract:
    Intestinal epithelial cell-derived interleukin (IL)-7 functions as a pleiotropic and nonredundant cytokine in the human intestinal mucosa; however, the molecular basis of its production has remained totally unknown. We here showed that human intestinal epithelial cells both constitutively and when induced by gamma interferon (IFN-gamma) produced IL-7, while several other factors we tested had no effect. Transcriptional regulation via an IFN regulatory factor element (IRF-E) on the 5' flanking region, which lacks canonical core promoter sequences, was pivotal for both modes of IL-7 expression. IRF-1 and IRF-2, the latter of which is generally known as a transcriptional repressor, were shown to interact with IRF-E and transactivate IL-7 gene expression in an IFN-gamma-inducible and constitutive manner, respectively. Indeed, tetracycline-inducible expression experiments revealed that both of these IRF proteins up-regulated IL-7 protein production, and their exclusive roles were further confirmed by small interfering RNA-mediated gene silencing systems. Moreover, these IRFs displayed distinct properties concerning the profile of IL-7 transcripts upon activation and expression patterns within human colonic epithelial tissues. These results suggest that the functional interplay between IRF-1 and IRF-2 serves as an elaborate and cooperative mechanism for timely as well as continuous regulation of IL-7 production that is essential for local immune regulation within human intestinal mucosa.
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