Clark A J
Division of Molecular Biology, Roslin Institute, Midlothian, Scotland, U.K.
Biochem Soc Symp. 1998;63:133-40.
The gene encoding the milk protein beta-lactoglobulin in sheep is expressed in the mammary gland in a tissue-specific manner during pregnancy and lactation. The unmodified sheep gene behaves appropriately in transgenic mice, and we have shown that many of the cis-acting elements that mediate this pattern of expression are located in the proximal 400 bp of the promotor. Using a combination of approaches we have identified a number of discrete cis-acting elements and their corresponding trans-acting factors that control the responsiveness of this gene in vivo. The beta-lactoglobulin promoter elements can be used to target the expression of foreign genes to the mammary gland in transgenic mice. We have used this approach in basic studies of mammary gland biology and for the production of therapeutic proteins in the milk of transgenic animals. In these circumstances, however, the promoter rarely functions optimally, and it may even be silenced; consequently, we have had to develop a number of strategies to overcome this problem. Nevertheless, foreign proteins do appear to be appropriately post-translationally modified when they are expressed in the mammary gland.
绵羊中编码乳蛋白β-乳球蛋白的基因在怀孕和哺乳期间以组织特异性方式在乳腺中表达。未修饰的绵羊基因在转基因小鼠中表现正常，并且我们已经表明，介导这种表达模式的许多顺式作用元件位于启动子的近端400bp内。通过多种方法相结合，我们已经鉴定出一些离散的顺式作用元件及其相应的反式作用因子，它们在体内控制该基因的反应性。β-乳球蛋白启动子元件可用于将外源基因的表达靶向转基因小鼠的乳腺。我们已将这种方法用于乳腺生物学的基础研究以及在转基因动物的乳汁中生产治疗性蛋白质。然而，在这些情况下，启动子很少能最佳发挥作用，甚至可能被沉默；因此，我们不得不制定一些策略来克服这个问题。尽管如此，当外源蛋白质在乳腺中表达时，它们确实似乎经过了适当的翻译后修饰。
