Le Ricousse S, Gouilleux F, Fortin D, Joulin V, Richard-Foy H
Unité de Recherche sur les Communication Hormonales de I'Institut National de la Santé et de la Recherche Médicale, Bicêtre, France.
Proc Natl Acad Sci U S A. 1996 May 14;93(10):5072-7. doi: 10.1073/pnas.93.10.5072.
We have previously characterized a regulatory element located between -294 and -200 within the mouse mammary tumor virus (MMTV) long terminal repeat (LTR). This element termed AA element cooperates with the glucocorticoid response elements (GREs) for glucocorticoid activation. Here we show that in a MMTV LTR wild type context, the deletion of this element significantly reduces both glucocorticoid and progestin activation of the promoter. Deletion of the two most distal GREs forces the glucocorticoid receptor (GR) and the progestin receptor (PR) to bind the same response elements and results in a dramatic decrease in the inducibility of the MMTV promoter by the two hormones. The simultaneous deletion of the two distal GREs and of the AA element abolishes completely the glucocorticoid-induced activation of the promoter. In contrast it restores a significant level of progestin-induced activation. This different effect of the double deletion on glucocorticoid- and progestin-induced MMTV promoter activation is not cell specific because it is also observed, and is even stronger, when either GR or PR is expressed in the same cell line (NIH 3T3). This is the first description of a mutated MMTV promoter that, although retaining GREs, is activated by progestins and not by glucocorticoids. This suggests a different functional cooperation between protein(s) interacting with the AA element and GR or PR. Cotransfections with constructs containing wild-type or mutated MMTV LTR with either PR lacking its C-terminal domain or GR/PR chimeras in which the N-terminal domains have been exchanged demonstrate that the N-terminal domains of the receptors specify the different behavior of GR and PR regarding the AA element.
我们之前已对位于小鼠乳腺肿瘤病毒（MMTV）长末端重复序列（LTR）中-294至-200之间的一个调控元件进行了特征描述。这个被称为AA元件的元件与糖皮质激素反应元件（GREs）协同作用以实现糖皮质激素激活。在此我们表明，在MMTV LTR野生型背景下，该元件的缺失显著降低了启动子的糖皮质激素和孕激素激活。两个最远端GREs的缺失迫使糖皮质激素受体（GR）和孕激素受体（PR）结合相同的反应元件，并导致两种激素对MMTV启动子诱导性的显著降低。两个远端GREs和AA元件的同时缺失完全消除了糖皮质激素诱导的启动子激活。相反，它恢复了显著水平的孕激素诱导激活。这种双重缺失对糖皮质激素和孕激素诱导的MMTV启动子激活的不同影响并非细胞特异性的，因为当GR或PR在同一细胞系（NIH 3T3）中表达时也能观察到，且这种影响甚至更强。这是对一种突变的MMTV启动子的首次描述，该启动子尽管保留了GREs，但由孕激素而非糖皮质激素激活。这表明与AA元件相互作用的蛋白质与GR或PR之间存在不同的功能协同作用。用含有野生型或突变型MMTV LTR的构建体与要么缺少其C末端结构域的PR要么N末端结构域已交换的GR/PR嵌合体进行共转染表明，受体的N末端结构域决定了GR和PR在AA元件方面的不同行为。
