A putative silencer element in the IL-5 gene recognized by Bcl6
A putative silencer element in the IL-5 gene recognized by Bcl6
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DOI：
10.4049/jimmunol.169.2.829
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发表时间：
2002-07-15
影响因子：
4.4
通讯作者：
Tokuhisa, T
中科院分区：
文献类型：
--
作者：
Arima, M;Toyama, H;Tokuhisa, T
Bcl6基因在成年小鼠组织中普遍表达，其产物作为一种序列特异性转录抑制因子发挥作用。Bcl6基因缺陷的小鼠表现出由Th2细胞因子过度产生引起的嗜酸性粒细胞炎症。Bcl6对这些细胞因子产生的调节机制存在争议。当用抗CD3抗体刺激来自Bcl6缺陷型和lck - Bcl6转基因小鼠的CD4(+) T细胞时，在Th2型细胞因子中，IL - 5的产生优先受到T细胞中Bcl6含量的影响。我们在小鼠和人类IL - 5基因的3'非翻译区发现了一个假定的Bcl6结合序列（IL5BS），并且通过凝胶阻滞试验和染色质免疫沉淀试验证实了Bcl6蛋白与该序列的特异性结合。在抗CD3刺激后，内源性Bcl6的结合活性在Th2克隆中短暂降低，但在Th1克隆中没有。外源性Bcl6抑制了K562细胞中带有IL5BS的报告基因的表达，并且由于IL5BS的一个点突变，抑制活性丧失。此外，IL5BS是Bcl6抑制IL - 5 cDNA表达所必需的。因此，IL5BS可能作为Bcl6的一个沉默元件来抑制IL - 5基因的表达。
The Bcl6 gene is ubiquitously expressed in adult murine tissues and its product functions as a sequence-specific transcriptional repressor. Bcl6-deficient mice displayed eosinophilic inflammation caused by overproduction of Th2 cytokines. The regulatory mechanism of those cytokine productions by Bcl6 is controversial. When CD4(+) T cells from Bcl6-deficient and lck-Bcl6-transgenic mice were stimulated with anti-CD3 Abs, production of IL-5 among Th2 type cytokines was preferentially affected by the amount of Bcl6 in the T cells. We found a putative Bcl6-binding sequence (IL5BS) on the 3' untranslated region in the murine and human IL-5 genes, and specific binding of Bcl6 protein to the sequence was confirmed by gel retardation assay and chromatin immunoprecipitation assay. The binding activity of endogenous Bc16 was transiently diminished in Th2 but not in Th1 clones after anti-CD3 stimulation. The exogenous Bc16 repressed expression of the reporter gene with the 1L5BS in K562 cells and the repressor activity was lost by a point mutation of the IL5BS. Furthermore, the IL5BS was required for Bc16 to repress expression of the IL-5 cDNA. Thus, the IL5BS may act as a silencer element for Bcl6 to repress expression of the IL-5 gene.