Ray A, Hannink M, Ray B K
Department of Veterinary Microbiology, University of Missouri, Columbia 65211, USA.
J Biol Chem. 1995 Mar 31;270(13):7365-74. doi: 10.1074/jbc.270.13.7365.
The promoter region of the rabbit serum amyloid A (SAA) gene contains two adjacent C/EBP and one NF-kappa B binding element. Involvement of these elements in SAA gene induction, following lipopolysaccharide (LPS) stimulation of the liver, has been studied by investigating LPS-activated transcription factors and their interaction with the promoter elements of the SAA gene. Appearance of complexes in the electrophoretic mobility shift assay has indicated that DNA-binding proteins that interact with the NF-kappa B element of the SAA promoter are induced in the LPS-treated rabbit liver. Presence of RelA (p65 subunit of NF-kappa B) in these complexes was demonstrated by the ability of RelA-specific antisera to supershift the DNA-protein complexes. LPS also induced several members of the C/EBP family of transcription factors, which interacted with the C/EBP motifs of the SAA promoter. Activated C/EBP and RelA form a RelA-C/EBP heteromeric complex that associates with varying affinity to NF-kappa B and C/EBP elements of the SAA gene. Transfection assays using both transcription factor genes have demonstrated that the heteromeric complex of NF-kappa B and C/EBP is a much more potent transactivator of SAA expression than each transcription factor alone. The heteromeric complex efficiently promotes transcription from both NF-kappa B and C/EBP sites.
兔血清淀粉样蛋白A（SAA）基因的启动子区域包含两个相邻的C/EBP和一个NF-κB结合元件。通过研究脂多糖（LPS）刺激肝脏后这些元件在SAA基因诱导中的作用，对LPS激活的转录因子及其与SAA基因启动子元件的相互作用进行了研究。电泳迁移率变动分析中复合物的出现表明，与SAA启动子的NF-κB元件相互作用的DNA结合蛋白在LPS处理的兔肝脏中被诱导。通过RelA特异性抗血清使DNA-蛋白质复合物超迁移的能力，证明了这些复合物中存在RelA（NF-κB的p65亚基）。LPS还诱导了与SAA启动子的C/EBP基序相互作用的几种C/EBP转录因子家族成员。活化的C/EBP和RelA形成RelA-C/EBP异源复合物，该复合物以不同亲和力与SAA基因的NF-κB和C/EBP元件结合。使用两种转录因子基因的转染分析表明，NF-κB和C/EBP的异源复合物比单独的每个转录因子都是更强有力的SAA表达反式激活因子。该异源复合物有效地促进了来自NF-κB和C/EBP位点的转录。
