Bcl6 is a transcriptional repressor for the IL-18 gene
Bcl6 is a transcriptional repressor for the IL-18 gene
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DOI：
10.4049/jimmunol.171.1.426
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发表时间：
2003-07-01
影响因子：
4.4
通讯作者：
Tokuhisa, T
中科院分区：
文献类型：
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作者：
Takeda, N;Arima, M;Tokuhisa, T
Bc16 作为序列特异性转录抑制因子发挥作用，据报道，Bc16 缺陷型 (Bc16(-/-)) 小鼠在多个器官中表现出 Th2 型炎症性疾病。由于IL-18是Th2细胞的有效刺激剂，我们检测了LPS刺激后Bc16(-/-)小鼠骨髓源性巨噬细胞中IL-18 mRNA的表达。在这里，我们发现刺激后表达显着上调。通过转染显性失活型 Bc16 基因，该表达在小鼠巨噬细胞系 RAW264 细胞中也上调。我们在鼠 IL-18 基因的外显子 1 上游鉴定了一个推定的 Bc16 结合 DNA 序列 (IL-18BS)，在人 IL-18 基因的启动子区域鉴定了三个 EL-18BS。通过凝胶阻滞试验和染色质免疫沉淀试验检测静息RAW264细胞核蛋白中的Bc16与鼠IL-18BS的结合。 LPS刺激后RAW264细胞中的结合活性逐渐减弱。然而，这些细胞中 Bc16 蛋白的量在检查期间保持恒定，表明刺激后 Bc16 蛋白发生功能修饰。此外，Bc16 需要鼠 IL-18BS 来抑制 IL-18 启动子控制下的荧光素酶报告基因的表达。总的来说，Bc16 是巨噬细胞产生 IL-18 的关键调节因子。
Bc16 functions as a sequence-specific transcriptional repressor, and Bc16-deficient (Bc16(-/-)) mice have been reported to display Th2-type inflammatory diseases in multiple organs. Since IL-18 is a potent stimulator of Th2 cells, we examined the expression of IL-18 mRNA in bone marrow-derived macrophages from Bc16(-/-) mice after LPS stimulation. Here we show that the expression was strikingly up-regulated after stimulation. The expression was also up-regulated in RAW264 cells, a murine macrophage cell line, by transfection with the dominant negative type of Bc16 gene. We identified a putative Bc16-binding DNA sequence (IL-18BS) upstream of exon 1 of the murine IL-18 gene and three EL-18BSs in the promoter region of human IL-18 gene. Binding of Bc16 in nuclear protein from resting RAW264 cells to murine IL-18BS was detected by gel retardation assay and chromatin immunoprecipitation assay. The binding activity was diminished gradually in RAW264 cells after LPS stimulation. However, the amount of Bc16 protein in these cells was constant over the period examined, suggesting the functional modification of Bc16 protein after stimulation. Furthermore, murine IL-18BS was required for Bc16 to repress the expression of the luciferase reporter gene under control of the IL-18 promoter. Taken together, Bc16 is a key regulator of IL-18 production by macrophages.