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Molecular and Cellular Biology, July 2004, p. 6298-6310, Vol. 24, No. 14
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.14.6298-6310.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Tetsuya Nakamura,1,
Shin Namiki,1 Eriko Okada,1 Kiichiro Tsuchiya,1 Ryuichi Okamoto,1 Motomi Yamazaki,1 Takanori Yokota,2 Masatoshi Aida,3 Yuki Yamaguchi,3 Takanori Kanai,1 Hiroshi Handa,3 and Mamoru Watanabe1*
Department of Gastroenterology and Hepatology,1 Department of Neurology and Neurological Sciences, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8519,2 Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan3
Received 10 September 2003/ Returned for modification 16 January 2004/ Accepted 19 April 2004
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-
) 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-
-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.
S.O. and T.N. contributed equally to this work.
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