Crucial roles of binding sites for NF-κB and C/EBPs in IκB-ζ-mediated transcriptional activation

Abstract

IκB-ζ [inhibitor of NF-κB (nuclear factor κB) ζ ] is a nuclear protein that is induced upon stimulation of TLRs (Toll-like receptors) and IL (interleukin)-1 receptor. IκB-ζ harbours Cterminal ankyrin repeats that interact with NF-κB. Our recent studies have shown that, upon stimulation, IκB-ζ is essential for the induction of a subset of inflammatory genes, represented by IL-6, whereas it inhibits the expression of TNF (tumour necrosis factor)-α. In the present study, we investigated mechanisms that determine the different functions of IκB-ζ . We found that coexpression of IκB-ζ and the NF-κB subunits synergistically activates transcription of the hBD-2 (human β-defensin 2) and NGAL (neutrophil gelatinase-associated lipocalin) genes, whereas it inhibits transcription of E-selectin. Reporter analyses indicated that, in addition to an NF-κB-binding site, a flanking C/EBP (CCAAT/enhancer-binding protein)-binding site in the promoters is essential for the IκB-ζ -mediated transcriptional activation. Using an artificial promoter consisting of the NF-κB-and C/EBP-binding sites, transcriptional activation was observed upon co-transfection with IκB-ζ and NF-κB, indicating that these sequences are minimal elements that confer the IκB-ζ -mediated transcriptional activation. Chromatin immunoprecipitation assays and knockdown experiments showed that both IκB-ζ and the NF-κB subunits were recruited to the NGAL promoter and were essential for the transcriptional activation of the hBD-2 and NGAL promoters on stimulation with IL-1β. The activation of the NGAL promoter by transfection of IκB-ζ and NF-κB was suppressed in C/EBPβ-depleted cells. Thus IκB-ζ acts as an essential transcriptional activator by forming a complex with NF-κB on promoters harbouring the NF-κB-and C/EBP-binding sites, upon stimulation of TLRs or IL-1 receptor.Key words: CCAAT/enhancer-binding protein (C/EBP), inflammation, inhibitor of nuclear factor κB ζ (IκB-ζ ), innate immunity, nuclear factor κB (NF-κB), transcription.

IκBζ is a key driver in the development of psoriasis

“…IκBζ has previously been demonstrated to be highly expressed in Th17 cells, dendritic cells, and macrophages upon TLR stimulation, whereas IκBζ is barely detectable in resting cells (18,31). In agreement with a previous study (10), we found that IκBζ was highly expressed in human keratinocytes upon IL-17A stimulation, whereas TNFα stimulation had only a minor effect on IκBζ expression.…”

The myxoid liposarcoma FUS-DDIT3 fusion oncoprotein deregulates NF-κB target genes by interaction with NFKBIZ

“…Furthermore, overexpression of NFKBIZ in HT1080 cells resulted in elevated IL8 transcription, indicating a role for NFKBIZ. This interpretation is further supported by a recent report showing that NFKBIZ binds and acts on a composite or adjacent C/EBP-NF-kB site almost identical to the site investigated in this study (Matsuo et al, 2007).…”

Rapid Myeloid Cell Transcriptional and Proteomic Responses to Periodontopathogenic Porphyromonas gingivalis

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