Wu K J, Wilson D R, Shih C, Darlington G J
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
J Biol Chem. 1994 Jan 14;269(2):1177-82.
HNF1 and C/EBP alpha are transcription factors that bind to and trans-activate the human albumin gene proximal promoter. Various 5' deletions of the human albumin promoter were coupled to a luciferase reporter gene (alb-luc constructs) and co-electroporated with HNF1 and/or C/EBP alpha expression vectors into HeLa cells. Luciferase activities from co-electroporation of the HNF1 and C/EBP alpha expression vectors with the alb-luc constructs were approximately 10-fold greater than the sum of the activities achieved with HNF1 and C/EBP alpha alone. Analysis of COOH-terminal or internal deletions of the HNF1 expression vector revealed that the domain important for collaborative interaction with C/EBP alpha could be localized to a 157 amino acid region not previously described. This domain is proline and glutamine-rich and is highly homologous (66%) to a portion of vHNF1, an evolutionarily related gene first identified in dedifferentiated hepatoma cells. A construct linking the negatively charged activation domain of herpes simplex virus protein VP16 to the DNA-binding domain of HNF1 showed that it could also synergize with C/EBP alpha to trans-activate the human albumin gene promoter. Our studies delineate a domain in HNF1 important for synergistic activation with C/EBP alpha.
肝细胞核因子1（HNF1）和CCAAT增强子结合蛋白α（C/EBPα）是与人类白蛋白基因近端启动子结合并反式激活该启动子的转录因子。将人类白蛋白启动子的各种5'端缺失片段与荧光素酶报告基因（alb-luc构建体）相连，并与HNF1和/或C/EBPα表达载体共电穿孔导入HeLa细胞。HNF1和C/EBPα表达载体与alb-luc构建体共电穿孔后的荧光素酶活性比单独使用HNF1和C/EBPα时所获得活性之和大约高10倍。对HNF1表达载体的羧基末端或内部缺失进行分析表明，与C/EBPα协同相互作用的重要结构域可定位到一个此前未描述过的157个氨基酸区域。该结构域富含脯氨酸和谷氨酰胺，并且与vHNF1的一部分高度同源（66%），vHNF1是在去分化肝癌细胞中首次鉴定出的一个进化相关基因。一个将单纯疱疹病毒蛋白VP16带负电荷的激活结构域与HNF1的DNA结合结构域相连的构建体表明，它也能与C/EBPα协同反式激活人类白蛋白基因启动子。我们的研究确定了HNF1中一个对与C/EBPα协同激活很重要的结构域。
