DISRUPTION OF A BINDING-SITE FOR HEPATOCYTE NUCLEAR FACTOR-IV RESULTS IN HEMOPHILIA-B LEYDEN
DISRUPTION OF A BINDING-SITE FOR HEPATOCYTE NUCLEAR FACTOR-IV RESULTS IN HEMOPHILIA-B LEYDEN
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DOI：
10.1073/pnas.89.14.6300
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发表时间：
1992-07-15
影响因子：
11.1
通讯作者：
REITSMA, PH
中科院分区：
文献类型：
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作者：
REIJNEN, MJ;SLADEK, FM;REITSMA, PH
血友病B-莱登是一种X染色体连锁的出血性疾病，其特征是儿童时期血浆凝血因子IX(FIX)水平非常低。青春期后，血浆FIX水平逐渐上升到正常水平的60%，这可能是在睾丸素的影响下。血友病B Leyden患者FIX启动子区域的单点突变已被报道在-20、-6、-5、+8和+13。此外，还检测到一个启动子突变(G->；C at-26)，该突变可使FIX表达终生取消(M.Ludwig，Personal Communication)。我们研究了血友病B Leyden突变之一(T-&Gt；A at-20)和G-->；C突变-26是如何干扰FIX基因转录的。我们报道了人FIX基因的野生型启动子包含一个肝细胞核因子4(HNF-4)的结合位点(在-34到-10位核苷酸)，HNF-4是类固醇激素受体超家族转录因子的成员之一。HNF-4的结合被-20处的T-->；A突变和-26处的G-->；C突变所破坏。虽然HNF-4在肝脏(HepG2)和非肝脏(HeLa)细胞类型中对野生型启动子序列有很好的反式激活作用，但它对-20突变启动子的反式激活作用有限，对-26突变启动子的反式激活作用则完全不是。这些数据表明，在正常人中，HNF-4是控制FIX表达的主要因素，它不能有效地与-20T->；A和-26G-->；C突变启动子序列结合导致血友病。此外，血友病表型的严重程度似乎与HNF-4结合和反式激活的破坏程度直接相关。
Hemophilia B Leyden is an X chromosome-linked bleeding disorder characterized by very low plasma levels of blood coagulation factor IX (fIX) during childhood. After puberty, plasma fIX levels gradually rise to a maximum of 60% of normal, probably under the influence of testosterone. Single point mutations in the fIX promoter region of hemophilia B Leyden patients have been reported at -20, -6, -5, +8 and +13. In addition, one promoter mutation (G --> C at -26) has been detected that abolishes fIX expression throughout life (M. Ludwig, personal communication). We examined how one of the hemophilia B Leyden mutations (T --> A at -20) and the G --> C mutation at -26 interfere with fIX gene transcription. We report that the wild-type promoter of the human fIX gene contains a binding site (at nucleotides -34 to -10) for hepatocyte nuclear factor 4 (HNF-4), a member of the steroid hormone receptor superfamily of transcription factors. The binding of HNF-4 is disrupted by both the T --> A mutation at -20 and the G --> C mutation at -26. Whereas HNF-4 transactivates the wild-type promoter sequence in liver (HepG2) and non-liver (HeLa) cell types quite well, it transactivates the -20 mutated promoter to only a limited extent and the -26 mutated promoter not at all. These data suggest that HNF-4 is a major factor controlling fIX expression in the normal individual and that its inability to bind efficiently to the -20 T --> A and the -26 G --> C mutated promoter sequence results in hemophilia. Further, the severity of the hemophilia phenotype appears to be directly related to the degree of disruption of HNF-4 binding and transactivation.