Interaction between the homeodomain proteins Cdx2 and HNF1α mediates expression of the lactase-phlorizin hydrolase gene
Interaction between the homeodomain proteins Cdx2 and HNF1α mediates expression of the lactase-phlorizin hydrolase gene
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DOI：
10.1042/bj3460529
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发表时间：
2000-03
影响因子：
4.1
通讯作者：
C. Mitchelmore;J. Troelsen;N. Spodsberg;H. Sjöström;O. Norén
中科院分区：
文献类型：
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作者：
C. Mitchelmore;J. Troelsen;N. Spodsberg;H. Sjöström;O. Norén
乳糖酶-苯丙醇水解酶是一种刷边酶，它在小肠中特异表达，在小肠中水解牛奶中的主要碳水化合物乳糖。我们之前已经在转基因小鼠中证明了乳糖酶的组织特异性和发育性表达是由猪乳糖酶基因上游1 kb区域控制的。两种同源结构域转录因子，尾侧相关同源结构域蛋白（Cdx2）和肝核因子1α (hnf1α)，已知与几种肠道特异性基因（包括乳糖酶）启动子中的调节顺式元件结合，并且从发育早期就存在于哺乳动物肠上皮中。在本研究中，我们研究了Cdx2和hnf1 α是否物理相互作用并共同激活乳糖酶-苯丙醇水解酶启动子的转录。我们表明，这两个因子的存在导致转录水平比单独激活任一因子的总和高得多。Cdx2的n端激活域是与HNF1alpha最大协同作用所必需的。通过下拉实验，我们证实了Cdx2和HNF1alpha之间的直接蛋白-蛋白相互作用。相互作用结构域包括两种蛋白质的同源结构域。这是首次证明两种转录因子之间的功能相互作用参与了许多肠道特异性基因的激活。组织限制性因子之间的协同相互作用可能是加强肠道内发育和组织特异性基因表达的重要机制。
Lactase-phlorizin hydrolase is a brush-border enzyme which is specifically expressed in the small intestine where it hydrolyses lactose, the main carbohydrate found in milk. We have previously demonstrated in transgenic mice that the tissue-specific and developmental expression of lactase is controlled by a 1 kb upstream region of the pig lactase gene. Two homeodomain transcription factors, caudal-related homeodomain protein (Cdx2) and hepatic nuclear factor 1alpha (HNF1alpha), are known to bind to regulatory cis elements in the promoters for several intestine-specific genes, including lactase, and are present in mammalian intestinal epithelia from an early stage in development. In the present study, we examined whether Cdx2 and HNF1alpha physically interact and co-operatively activate transcription from the lactase-phlorizin hydrolase promoter. We show that the presence of both factors leads to a much higher level of transcription than the sum of the activation by either factor alone. The N-terminal activation domain of Cdx2 is required for maximal synergy with HNF1alpha. With the use of pull-down assays, we demonstrate a direct protein-protein interaction between Cdx2 and HNF1alpha. The interaction domain includes the homeodomain region of both proteins. This is the first demonstration of a functional interaction between two transcription factors involved in the activation of a number of intestine-specific genes. Synergistic interaction between tissue-restricted factors is likely to be an important mechanism for reinforcing developmental and tissue-specific gene expression within the intestine.