A novel NF-κB/Rel site in intron 1 cooperates with proximal promoter elements to mediate TNF-α-induced transcription of the human polymeric Ig receptor
A novel NF-κB/Rel site in intron 1 cooperates with proximal promoter elements to mediate TNF-α-induced transcription of the human polymeric Ig receptor
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DOI：
10.4049/jimmunol.167.11.6412
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发表时间：
2001-12-01
影响因子：
4.4
通讯作者：
Johansen, FE
中科院分区：
文献类型：
--
作者：
Schjerven, H;Brandtzaeg, P;Johansen, FE
分泌型抗体构成粘膜表面特异性免疫防御的第一道防线。这种抗体是由pIgR介导的聚合Ig （pIg）在分泌上皮上的主动转运产生的，也称为跨膜分泌成分（SC）。促炎细胞因子tnf - α是宿主对感染反应的关键介质，它可以刺激HT-29肠腺癌细胞系中pIgR/SC蛋白合成依赖性的转录上调。通过报告基因检测，我们在人类pIgRISC基因1内含子的748 bp片段中发现了一个新的tnf - α响应区域，该区域依赖于NF-kappaB/Rel位点实现完全响应。emsa显示NF-kappaB/Rel家族成员p65 （RelA）在tnf - α刺激后优先结合该DNA元件，而p50的结合更弱且更延迟。此外，内含子I中的tnf - α响应区域需要与位于基因近端启动子区域的DNA元件合作。突变分析表明，外显子I转录起始位点附近的ifn刺激反应元件参与了tnf - α反应。因此，在tnf - α诱导的pIgR/SC上调中，发现相距bbb40 kb的DNA元件相互配合。内含子tnf - α响应增强子与最近发现的il -4响应增强子重叠。在人类和小鼠pIgRISC基因之间，发现了几个在人类基因中具有重要功能的内含子DNA元件是高度保守的，这表明存在一个保守的细胞因子响应增强子区域。
Secretory Abs constitute the first line of specific immune defense at mucosal surfaces. Such Abs are generated by the active transport of polymeric Ig (pIg) across secretory epithelia mediated by the pIgR, also known as transmembrane secretory component (SC). The proinflammatory cytokine TNF-alpha is a key mediator of host responses to infections, and it can stimulate protein synthesis-dependent transcriptional up-regulation of pIgR/SC in the HT-29 intestinal adenocarcinoma cell line. By reporter gene assay we identified a novel TNF-alpha -responsive region located within a 748-bp fragment in intron 1 of the human pIgRISC gene which depended on an NF-kappaB/Rel site for full responsiveness. EMSAs demonstrated preferential binding of the NF-kappaB/Rel family member p65 (RelA) to this DNA element after TNF-alpha stimulation, with weaker and more delayed binding of p50. Furthermore, the TNF-alpha -responsive region in intron I required cooperation with DNA elements located in the proximal promoter region of the gene. Mutational analysis demonstrated that an IFN-stimuIated response element near the transcriptional start site in exon I was involved in the TNF-alpha responsiveness. Thus, DNA elements located >4 kb apart were found to cooperate in TNF-alpha -induced pIgR/SC up-regulation. The intronic TNF-alpha -responsive enhancer overlapped with a recently identified IL-4-responsive enhancer. Several intronic DNA elements found to be functionally important in the human gene are highly conserved between the human and mouse pIgRISC genes, suggesting the presence of a conserved cytokine-responsive enhancer region.