Howell B W, Lagacé M, Shore G C
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Mol Cell Biol. 1989 Jul;9(7):2928-33. doi: 10.1128/mcb.9.7.2928-2933.1989.
We have identified an essential cis element in the proximal promoter region of the rat carbamyl phosphate synthetase I (CPSI) gene that is requisite for promoter activity in liver nuclear extracts. Excess synthetic oligonucleotides specifying this region abolished promoter-dependent in vitro transcription. We show that C/EBP, a nuclear factor enriched in liver but found as well in other tissues, such as gut, fat, and lung, interacts with an inverted repeat, GTTGCAAC, at the core of the essential cis element. In brain, a tissue that did not express CPSI or contain significant levels of C/EBP, a different factor was capable of binding at or near the C/EBP recognition element. Activity of the CPSI promoter in liver nuclear extracts was also dependent on sequences 5' to the C/EBP motif; presumably, factors binding to elements within this upstream region are instrumental in restricting CPSI gene expression to liver and intestinal mucosa.
我们已在大鼠氨甲酰磷酸合成酶I（CPSI）基因近端启动子区域鉴定出一个必需的顺式元件，该元件对于肝核提取物中的启动子活性是必需的。过量合成的指定该区域的寡核苷酸消除了启动子依赖性的体外转录。我们发现，C/EBP是一种在肝脏中富集但在其他组织（如肠道、脂肪和肺）中也存在的核因子，它与必需顺式元件核心处的反向重复序列GTTGCAAC相互作用。在大脑中，一个不表达CPSI或不含大量C/EBP的组织，一种不同的因子能够在C/EBP识别元件处或其附近结合。肝核提取物中CPSI启动子的活性也依赖于C/EBP基序5'端的序列；据推测，与该上游区域内元件结合的因子有助于将CPSI基因表达限制在肝脏和肠黏膜中。
