A role for CCAAT/enhancer-binding protein in hepatic expression of thrombin-activable fibrinolysis inhibitor
A role for CCAAT/enhancer-binding protein in hepatic expression of thrombin-activable fibrinolysis inhibitor
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DOI：
10.1074/jbc.m203688200
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发表时间：
2002-07-12
影响因子：
4.8
通讯作者：
Koschinsky, ML
中科院分区：
文献类型：
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作者：
Boffa, MB;Hamill, JD;Koschinsky, ML
凝血酶激活的纤溶抑制剂 (TAFI) 是一种羧肽酶 B 样酶原，在被凝血酶、凝血酶-血栓调节蛋白或纤溶酶激活后，通过抑制纤溶级联中的正反馈来减弱纤维蛋白凝块溶解。血浆中 TAFI 的浓度因人群而异，因此可能构成血栓性疾病的危险因素。此外，据报道，TAFI 在小鼠体内是一种阳性急性期反应物。我们已经开始对人类 TAFI 启动子进行分子分析，以了解 TAFI 基因表达调控的机制。我们在启动子的-53 和-40 之间鉴定了一个推定的C/EBP 结合位点。该位点的突变消除了 C/EBP 结合，使人肝癌 (HepG2) 细胞中的 TAFI 启动子活性降低了约 80%。 Get 迁移率变化分析表明 HepG2 核提取物中存在的 C/EBP-β 以及成年大鼠肝核提取物中存在的 C/EBP-a 和 -β 与 C/EBP 位点结合。 C/EBP-α、-β 和 -δ 亚型均能够结合 C/EBP 位点并激活 TAFI 启动子。人类 TAFI 启动子中功能性 C/EBP 结合位点的鉴定可能对该基因在发育过程中和炎症刺激反应中的表达调节具有重要意义。
Thrombin-activable fibrinolysis inhibitor (TAFI) is a procarboxypeptidase B-like zymogen that upon activation by thrombin, thrombin-thrombomodulin, or plasmin attenuates fibrin clot lysis by inhibiting positive feedback in the fibrinolytic cascade. The concentration of TAFI in plasma varies in the human population and thus may constitute a risk factor for thrombotic disorders. In addition, TAFI has been reported to be a positive acute phase reactant in mice. We have initiated molecular analysis of the human TAFI promoter to understand the mechanisms underlying regulation of TAFI gene expression. We identified a putative C/EBP-binding site between -53 and -40 of the promoter. Mutations in this site that abolish C/EBP binding decrease TAFI promoter activity in human hepatoma (HepG2) cells by similar to80%. Get mobility shift analyses indicated that C/EBP-beta present in HepG2 nuclear extracts and C/EBP-a and -beta present in adult rat liver nuclear extracts bind to the C/EBP site. C/EBP-alpha, -beta, and -delta isoforms are all capable of binding to the C/EBP site and activating the TAFI promoter. The identification of a functional C/EBP-binding site in the human TAFI promoter may have important implications for the regulation of expression of this gene during development and in response to inflammatory stimuli.