Crucial roles of binding sites for NF-κB and C/EBPs in IκB-ζ-mediated transcriptional activation
Crucial roles of binding sites for NF-κB and C/EBPs in IκB-ζ-mediated transcriptional activation
复制标题
DOI：
10.1042/bj20061797
复制
发表时间：
2007-08-01
影响因子：
4.1
通讯作者：
Muta, Tatsushi
中科院分区：
文献类型：
--
作者：
Matsuo, Susumu;Yamazaki, Soh;Muta, Tatsushi
I kappa B xi [NF-kappa B（核因子kappa B） xi的抑制剂]是一种核蛋白，在TLRs （toll样受体）和IL（白细胞介素）-1受体的刺激下诱导。我们最近的研究表明，在刺激下，I kappa B-xi对于诱导以IL-6为代表的炎症基因亚群至关重要，而它抑制TNF（肿瘤坏死因子）- α的表达。在本研究中，我们探讨了决定I kappa B-xi不同功能的机制。我们发现，I κ B-xi和nf - κ B亚基的共同表达协同激活hBD-2（人β -防御素2）和NGAL（神经嗜明胶酶相关脂质蛋白）基因的转录，而抑制e-选择素的转录。报道者分析表明，除了NF-kappa b结合位点外，启动子中侧侧的C/EBP （CCAAT/增强子结合蛋白）结合位点对于1 kappa B-xi介导的转录激活至关重要。使用由NF-kappa B-和C/ ebp结合位点组成的人工启动子，在与I kappa B-xi和NF-kappa B共转染时观察到转录激活，表明这些序列是赋予I kappa B-xi介导的转录激活的最小元件。染色质免疫沉淀试验和敲低实验表明，I κ pa B-xi和nf - κ pa B亚基都被募集到NGAL启动子上，并且对于IL-1 β刺激下hBD-2和NGAL启动子的转录激活是必不可少的。在C/EBP β -缺失细胞中，转染I κ pa B-xi和nf - κ pa B可抑制NGAL启动子的激活。因此，在TLRs或IL-1受体的刺激下，I kappa B-xi通过与NF-kappa B在含有NF-kappa B-和C/ ebp结合位点的启动子上形成复合物而发挥转录激活因子的作用。
I kappa B xi [inhibitor of NF-kappa B (nuclear factor kappa B) xi] is a nuclear protein that is induced upon stimulation of TLRs (Toll-like receptors) and IL (interleukin)-1 receptor. I kappa B-xi harbours C-terminal ankyrin repeats that interact with NF-kappa B. Our recent studies have shown that, upon stimulation, I kappa B-xi 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 I kappa B-xi. We found that co-expression Of I kappa B-xi and the NF-kappa B subunits synergistically activates transcription of the hBD-2 (human beta-defensin 2) and NGAL (neurtrophil gelatinase-associated lipocalin) genes, whereas it inhibits transcription of E-selectin. Reporter analyses indicated that, in addition to an NF-kappa B-binding site, a flanking C/EBP (CCAAT/enhancer-binding protein)-binding site in the promoters is essential for the 1 kappa B-xi -mediated transcriptional activation. Using an artificial promoter consisting of the NF-kappa B- and C/EBP-binding sites, transcriptional activation was observed upon co-transfection with I kappa B-xi and NF-kappa B, indicating that these sequences are minimal elements that confer the I kappa B-xi -mediated transcriptional activation. Chromatin immunoprecipitation assays and knockdown experiments showed that both I kappa B-xi and the NF-kappa B 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-1 beta. The activation of the NGAL promoter by transfection Of I kappa B-xi and NF-kappa B was suppressed in C/EBP beta-depleted cells. Thus I kappa B-xi acts as an essential transcriptional activator by forming a complex with NF-kappa B on promoters harbouring the NF-kappa B- and C/EBP-binding sites, upon stimulation of TLRs or IL-1 receptor.