GENES: STRUCTURE AND REGULATION
NF-IL6 (C/EBPβ) Vigorously Activates il1b Gene Expression via a Spi-1 (PU.1) Protein-Protein Tether*

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Two classes of transcription factors, ETS and bZIP, stand out as key mediators of monocyte commitment and differentiation. The ETS domain factor Spi-1 (also called PU.1) and the bZIP factor NF-IL6 (also called C/EBPβ) have been shown to be involved in the transcriptional regulation of interleukin-1β gene (il1b) and other monocyte-specific genes. We now show that these two factors strongly cooperate on the il1b core promoter (−59/+12) in the absence of direct NF-IL6 binding to DNA. Transient transfection assays, using mutated il1b core promoters, showed that the Spi-1, but not the NF-IL6, binding site is absolutely required for functional cooperativity. Furthermore, the NF-IL6 transactivation domain (TAD) is functionally indispensable and more critical than that of Spi-1. Additionally, TAD-deficient NF-IL6 functions as a dominant negative for Spi-1-mediated activation, suggesting the involvement of the bZIP DNA binding domain. This is supported by the demonstration of in vitro interaction between the NF-IL6 bZIP and Spi-1 winged helix-turn-helix (wHTH) DNA binding domains, arguing that NF-IL6 vigorously activates theil1b core promoter via protein-tethered transactivation mediated by Spi-1.

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Published, JBC Papers in Press, May 2, 2000, DOI 10.1074/jbc.M000145200

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This work was supported by National Institutes of Health Grant CA68544 (to P. E. A).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Recipient of the individual National Research Service Award.

Present address: Khon Kaen University, Faculty of Dentistry, Khon Kaen, Thailand 40002.

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Present address: First Dept. of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807, Japan.