Properties of the glucocorticoid modulatory element binding proteins GMEB-1 and-2: Potential new modifiers of glucocorticoid receptor transactivation and members of the family of KDWK proteins
Properties of the glucocorticoid modulatory element binding proteins GMEB-1 and-2: Potential new modifiers of glucocorticoid receptor transactivation and members of the family of KDWK proteins
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DOI：
10.1210/me.14.7.1010
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发表时间：
2000-07-01
影响因子：
--
通讯作者：
Simons, SS
中科院分区：
文献类型：
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作者：
Kaul, S;Blackford, JA;Simons, SS
糖皮质激素诱导酪氨酸氨基转移酶(TAT)基因表达的一个重要组成部分是糖皮质激素调节元件(GME)，它位于大鼠TAT基因的-3.6kb处。由于激动剂的剂量-反应曲线左移，GME既介导了对激素的更大敏感性，又增加了抗糖皮质激素的部分激动剂活性。GME的这些性质与两种蛋白质(GMEB-1和GMEB-2)的异构体复合体的结合密切相关。我们之前克隆了大鼠GMEB-2的67 kDa蛋白。我们现在报道GME结合复合体的另一个成员，88 kDa的人GMEB-1的克隆，以及这两种蛋白的各种性质。在哺乳动物的单杂交实验中，GMEB-1和GMEB-2都具有内在的反式激活活性，这与我们提出的修改糖皮质激素受体(GR)调节的基因诱导的模型是一致的。在哺乳动物双杂交和下拉试验中，GR与GMEB-1和GMEB-2之间的相互作用支持了这一假说。此外，GMEB-1和GMEB-2的过度表达，无论是单独的还是联合的，都会导致剂量-反应曲线的可逆右移，并降低抗类固醇的激动剂活性，正如其他限制因素被压制所预期的那样。在两种GMEB与CREB结合蛋白(CBP)的双杂交分析中的相互作用以及两种蛋白质中都没有组蛋白乙酰转移酶(HAT)活性，表明了与GME作用模型兼容的额外机制细节。GMEB-1和GMEB-2有一个90个氨基酸的序列，80%相同。该区域还显示出与包含KDWK核心序列的其他几种蛋白质的同源性。因此，GMEB可能是一个具有有趣转录特性的新的因子家族的成员。
An important component of glucocorticoid steroid induction of tyrosine aminotransferase (TAT) gene expression is the glucocorticoid modulatory element (GME), which is located at -3.6 kb of the rat TAT gene. The GME both mediates a greater sensitivity to hormone, due to a left shift in the dose-response curve of agonists, and increases the partial agonist activity of antiglucocorticoids. These properties of the GME are intimately related to the binding of a heteromeric complex of two proteins (GMEB-1 and -2). We previously cloned the rat GMEB-2 as a 67-kDa protein. We now report the cloning of the other member of the GME binding complex, the 88-kDa human GMEB-1, and various properties of both proteins. GMEB-1 and -2 each possess an intrinsic transactivation activity in mammalian one-hybrid assays, consistent with our proposed model in which they modify glucocorticoid receptor (GR)-regulated gene induction. This hypothesis is supported by interactions between GR and both GMEB-1 and -2 in mammalian two-hybrid and in pull-down assays. Furthermore, overexpression of GMEB-1 and -2, either alone or in combination, results in a reversible right shift in the dose-response curve, and decreased agonist activity of antisteroids, as expected from the squelching of other limiting factors. Additional mechanistic details that are compatible with the model of GME action are suggested by the interactions in a two-hybrid assay of both GMEBs with CREB-binding protein (CBP) and the absence of histone acetyl transferase (HAT) activity in both proteins. GMEB-1 and -2 share a sequence of 90 amino acids that is 80% identical. This region also displays homology to several other proteins containing a core sequence of KDWK. Thus, the GMEBs may be members of a new family of factors with interesting transcriptional properties.