| Abstract | IkappaB-zeta [inhibitor of NF-kappaB (nuclear factor kappaB) zeta] is a nuclear protein that is induced upon stimulation of TLRs (Toll-like receptors) and IL (interleukin)-1 receptor. IkappaB-zeta harbours C-terminal ankyrin repeats that interact with NF-kappaB. Our recent studies have shown that, upon stimulation, IkappaB-zeta 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)-alpha. In the present study, we investigated mechanisms that determine the different functions of IkappaB-zeta. We found that co-expression of IkappaB-zeta and the NF-kappaB subunits synergistically activates transcription of the hBD-2 (human beta-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-kappaB-binding site, a flanking C/EBP (CCAAT/enhancer-binding protein)-binding site in the promoters is essential for the IkappaB-zeta-mediated transcriptional activation. Using an artificial promoter consisting of the NF-kappaB- and C/EBP-binding sites, transcriptional activation was observed upon co-transfection with IkappaB-zeta and NF-kappaB, indicating that these sequences are minimal elements that confer the IkappaB-zeta-mediated transcriptional activation. Chromatin immunoprecipitation assays and knockdown experiments showed that both IkappaB-zeta and the NF-kappaB 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-1beta. The activation of the NGAL promoter by transfection of IkappaB-zeta and NF-kappaB was suppressed in C/EBPbeta-depleted cells. Thus IkappaB-zeta acts as an essential transcriptional activator by forming a complex with NF-kappaB on promoters harbouring the NF-kappaB- and C/EBP-binding sites, upon stimulation of TLRs or IL-1 receptor. |
| Authors | Susumu Matsuo, Soh Yamazaki, Koichiro Takeshige, Tatsushi Muta
(Affiliation: Department of Molecular and Cellular Biochemistry, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.)
|
| Journal | The Biochemical journal
(Biochem J)
Vol. 405
Issue 3
Pg. 605-15
(Aug 1 2007)
ISSN: 1470-8728 England |
| PMID | 17447895
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
|
| Chemical References |
- Acute-Phase Proteins
- CCAAT-Enhancer-Binding Proteins
- LCN2 protein, human
- Lipocalins
- NF-kappa B
- NFKBIZ protein, human
- Nuclear Proteins
- Proto-Oncogene Proteins
- RNA, Messenger
|
| Topics |
- Acute-Phase Proteins
(metabolism)
- Binding Sites
- CCAAT-Enhancer-Binding Proteins
(metabolism)
- Cell Line
- Humans
- Lipocalins
- NF-kappa B
(metabolism)
- Nuclear Proteins
(metabolism)
- Promoter Regions, Genetic
- Protein Binding
- Proto-Oncogene Proteins
(metabolism)
- RNA Interference
- RNA, Messenger
(metabolism)
- Transcription, Genetic
- Transcriptional Activation
|
