Kojima H, Nakajima K, Hirano T
Department of Molecular Oncology, Osaka University Medical School, Japan.
Oncogene. 1996 Feb 1;12(3):547-54.
The junB gene is one of immediate-early genes whose expression are regulated by a variety of extracellular stimuli and play important roles in cellular responses to the given stimuli. Interleukin-6 (IL-6) activates the junB promoter through an IL-6 response element, JRE-IL6, that is composed of two cooperative DNA motifs, a low affinity Stat-binding site overlapping with an Ets-binding site (JEBS) and a cAMP responsive element (CRE)-like site. This element is a target for the Jak-Stat signal transduction pathway. We showed that IL-6 induced novel complexes on JRE-IL6, termed JRE-IL6-BC1 and 2, which contained Stat3 but migrated more slowly than the complexes containing homo- or heterodimer of Stat3 and Stat1 in gel shift assays. These slow-migrating JRE-IL6-BCs appeared to contain CRE-like site binding proteins besides Stat3, since the formation of JRE-IL6-BCs required both the JEBS and CRE-like site of JRE-IL6 and oligonucleotides containing the CRE-like site or somatostatin CRE efficiently competed with JRE-IL6 for making JRE-IL6-BCs. The formation of the complexes correlated well with the responsiveness of JRE-IL6 to IL-6 signals. U.v.-cross linking study revealed that JRE-IL6 bound a 90 kDa protein, corresponding to Stat3, and a 36 kDa protein, most likely a CRE-like site binding protein(s). Furthermore, we showed that the IL-6/interferon gamma (IFN gamma) response element in the IRF-1 promoter (IR/IRF-1), which contains a Stat-binding site and an adjacent CRE-like site, also makes IL-6-induced binding complexes similar to JRE-IL6-BCs.
JunB基因是即刻早期基因之一，其表达受多种细胞外刺激调控，并在细胞对特定刺激的反应中发挥重要作用。白细胞介素-6（IL-6）通过一个IL-6反应元件JRE-IL6激活JunB启动子，该元件由两个协同的DNA基序组成，一个与Ets结合位点重叠的低亲和力Stat结合位点（JEBS）和一个类似cAMP反应元件（CRE）的位点。这个元件是Jak-Stat信号转导途径的靶点。我们发现IL-6在JRE-IL6上诱导形成了新的复合物，称为JRE-IL6-BC1和2，它们含有Stat3，但在凝胶迁移实验中比含有Stat3和Stat1同二聚体或异二聚体的复合物迁移得更慢。这些迁移缓慢的JRE-IL6-BC似乎除了Stat3外还含有类似CRE位点的结合蛋白，因为JRE-IL6-BC的形成需要JRE-IL6的JEBS和类似CRE的位点，并且含有类似CRE位点或生长抑素CRE的寡核苷酸能有效地与JRE-IL6竞争形成JRE-IL6-BC。复合物的形成与JRE-IL6对IL-6信号的反应性密切相关。紫外线交联研究表明，JRE-IL6结合了一个90 kDa的蛋白，对应于Stat3，以及一个36 kDa的蛋白，很可能是一种类似CRE位点的结合蛋白。此外，我们发现IRF-1启动子中的IL-6/干扰素γ（IFNγ）反应元件（IR/IRF-1），它含有一个Stat结合位点和一个相邻的类似CRE的位点，也能形成类似于JRE-IL6-BC的IL-6诱导的结合复合物。
