Glucocorticoid receptor domain requirements for chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter in different nucleoprotein contexts
Glucocorticoid receptor domain requirements for chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter in different nucleoprotein contexts
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DOI：
10.1074/jbc.m203898200
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发表时间：
2002-08-02
影响因子：
4.8
通讯作者：
Smith, CL
中科院分区：
文献类型：
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作者：
Keeton, EK;Fletcher, TM;Smith, CL
糖皮质激素受体(GR)包含几个激活结构域，tau1(AF-1)、tau2和AF-2，它们最初是使用瞬时转染的报告构建体来定义的。利用全长GR中的结构域突变，本研究定义了在两种不同的核蛋白配置中激活小鼠乳腺肿瘤病毒(MMTV)启动子所需的结构域。瞬时转染的MMTV模板具有无序的、可访问的染色质结构，在很大程度上依赖于AF-2结构域的激活。相反，在有组织的、复制的染色质中激活MMTV模板需要这两个结构域，但对tau1结构域的依赖性相对较大。还研究了GR诱导的后一种模板染色质重塑的结构域要求。AF-2螺旋12结构域的突变部分抑制了核酸酶超敏反应的诱导，但在没有tau1的情况下这种抑制作用被解除，这表明这两个结构域之间发生了重要的相互作用。进一步的突变分析表明，GR诱导的染色质重塑需要螺旋3区域的配体结合结构域。我们的研究表明，靶启动子转录调控所需的GR激活面部分取决于其染色质结构。在特定的细胞环境中，GR似乎在激活靶启动子的机制上具有显着程度的多功能性。
The glucocorticoid receptor (GR) contains several activation domains, tau1 (AF-1), tau2, and AF-2, which were initially defined using transiently transfected reporter constructs. Using domain mutations in the context of full-length GR, this study defines those domains required for activation of the mouse mammary tumor virus (MMTV) promoter in two distinct nucleoprotein configurations. A transiently transfected MMTV template with a disorganized, accessible chromatin structure was largely dependent on the AF-2 domain for activation. In contrast, activation of an MMTV template in organized, replicated chromatin requires both domains but has a relatively larger dependence on the tau1 domain. Domain requirements for GR-induced chromatin remodeling of the latter template were also investigated. Mutation of the AF-2 helix 12 domain partially inhibits the induction of nuclease hypersensitivity, but the inhibition was relieved in the absence of tau1, suggesting the occurrence of an important interaction between the two domains. Further mutational analysis indicates that GR-induced chromatin remodeling requires the ligand-binding domain in the region of helix 3. Our study shows that the GR activation surfaces required for transcriptional modulation of a target promoter were determined in part by its chromatin structure. Within a particular cellular environment the GR appears to possess a significant degree of versatility in the mechanism by which it activates a target promoter.