Li S P, Liu T Y, Goldman N D
Division of Biochemistry and Biophysics, Food and Drug Administration, Bethesda, Maryland.
J Biol Chem. 1990 Mar 5;265(7):4136-42.
To study the mechanism of induction of human C-reactive protein (CRP) gene expression, we have utilized an in vitro liver cell system to analyze the cis-acting DNA sequences located within the 5'-flanking region of human CRP gene. Stable transfection of human hepatoma cells, PLC/PRF/5, by a CRP gene construct containing the 1 kilobase pair of upstream sequence of the CRP gene demonstrated that this region contained the inducible element(s) which regulated human CRP gene transcription. Dissection of this region by 5', 3' and internal deletion constructs of upstream region of the CRP gene fused to a reporter gene, chloramphenicol acetyl transferase, indicated the presence of two inducible elements located proximal to the site of initiation of transcription, two constitutive enhancer-like elements located distal to the promoter, and a negative regulatory region located between the two inducible elements. We had previously shown that a protein factor from monocytes or HTLV1-infected T-cells, was responsible for CRP induction in hepatoma cells. We have found this factor to be synonymous with interleukin-6. By stable and transient transfection assays in hepatoma cells, recombinant interleukin-6 alone was sufficient to activate both inducible elements.
为研究人类C反应蛋白（CRP）基因表达的诱导机制，我们利用体外肝细胞系统分析了位于人类CRP基因5'侧翼区域内的顺式作用DNA序列。用含有CRP基因1千碱基对上游序列的CRP基因构建体对人肝癌细胞PLC/PRF/5进行稳定转染，结果表明该区域含有调节人类CRP基因转录的诱导元件。通过将CRP基因上游区域的5'、3'和内部缺失构建体与报告基因氯霉素乙酰转移酶融合，对该区域进行剖析，结果表明在转录起始位点近端存在两个诱导元件，在启动子远端存在两个组成型增强子样元件，并且在两个诱导元件之间存在一个负调控区域。我们之前已经表明，来自单核细胞或HTLV1感染的T细胞的一种蛋白质因子负责肝癌细胞中CRP的诱导。我们发现这种因子与白细胞介素-6同义。通过在肝癌细胞中的稳定和瞬时转染试验，单独的重组白细胞介素-6足以激活这两个诱导元件。
