Addison W R, Kurtz D T
Department of Genetics, University of Alberta, Edmonton, Canada.
J Biol Chem. 1989 Dec 25;264(36):21891-5.
The induction of rat alpha 2u-globulin by glucocorticoids is a secondary response to the hormone, that is protein synthesis is absolutely required for induction. Using the DNase I protection assay, we have identified three proteins present in rat liver nuclei that bind in or near the regulatory region of a cloned alpha 2u-globulin gene. One protein which we term alpha 2u-globulin nuclear factor 1 (alpha 2uNF1), binds to precisely the sequence we have previously shown to be required for hormonal induction. Genes containing linker-scanning mutations in this region show diminished binding to this nuclear factor and display greatly reduced or abolished glucocorticoid response. alpha 2uNF1 was detected in nuclei from several sources, and its level is apparently unaffected by glucocorticoids. Its recognition sequence is unlike those of previously reported transcription factors. We detect two other proteins, alpha 2uNF2 and alpha 2uNF3, that bind near the alpha 2u-globulin regulatory region. A mutant alpha 2u-globulin promoter which does not bind alpha 2uNF2 shows increased inducibility by glucocorticoids in transfected mouse L-cells. The binding of alpha 2uNF3 is not required for alpha 2u-globulin induction by the hormone.
糖皮质激素诱导大鼠α2u球蛋白是该激素的一种次级反应，也就是说诱导过程绝对需要蛋白质合成。利用DNA酶I保护试验，我们在大鼠肝细胞核中鉴定出三种蛋白质，它们结合在克隆的α2u球蛋白基因调控区或其附近。我们将其中一种蛋白质称为α2u球蛋白核因子1（α2uNF1），它精确地结合在我们先前证明的激素诱导所需序列上。在该区域含有连接子扫描突变的基因与这种核因子的结合减少，并且糖皮质激素反应大大降低或消失。在来自多个来源的细胞核中检测到α2uNF1，其水平显然不受糖皮质激素影响。其识别序列与先前报道的转录因子不同。我们还检测到另外两种蛋白质，α2uNF2和α2uNF3，它们结合在α2u球蛋白调控区附近。一个不与α2uNF2结合的突变α2u球蛋白启动子在转染的小鼠L细胞中对糖皮质激素的诱导性增加。激素诱导α2u球蛋白不需要α2uNF3的结合。
