Nuclear factor 1 is required for both hormone-dependent chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter
Nuclear factor 1 is required for both hormone-dependent chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter
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DOI：
10.1128/mcb.23.3.887-898.2003
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发表时间：
2003-02-01
影响因子：
5.3
通讯作者：
Archer, TK
中科院分区：
文献类型：
--
作者：
Hebbar, PB;Archer, TK
小鼠乳腺肿瘤病毒（MMTV）启动子已被用作模型来研究糖皮质激素受体（GR）如何重塑染色质以允许其他转录因子结合并激活转录。为了剖析核因子 1 (NF1) 在染色质重塑和转录激活中的精确作用，我们使用 MMTV 启动子上转录因子结合位点的接头扫描突变体。我们在瞬时转染模板（瞬时转染）和染色质组织模板（稳定转染）的背景下比较了 NF1 突变 MMTV 启动子，以了解染色质对因子结合和转录的影响。我们发现，在瞬时转染的模板上，NF1 结合位点的突变会减少基础转录和激素依赖性转录。这表明在缺乏有组织的染色质的情况下转录需要 NF1。我们还发现 NF1 在瞬时转染模板上的结合与激素反应元件或八聚体转录因子 (OTF) 结合位点的突变无关。相反，OTF 蛋白与瞬时转染模板的结合被发现依赖于 NF1 的结合，这可能意味着 NF1 对 OTF 结合具有稳定作用。在染色质模板上，NF1 结合位点的突变不会影响核小体在启动子上的定位。我们还发现，在没有 NF1 结合的情况下，GR 介导的核小体 B 染色质重塑会减少，激素依赖性转录激活也会被消除。此外，我们证明 NF1 对于 BRG1 染色质重塑复合物和体内启动子上的 GR 的结合都是必需的。这些结果表明，NF1 除了直接增强转录之外，还可能参与染色质重塑活动，并且在缺乏其结合位点的情况下，GR 无法有效结合启动子并招募重塑复合物。
The mouse mammary tumor virus (MMTV) promoter has been used as a model to study how the glucocorticoid receptor (GR) remodels chromatin to allow other transcription factors to bind and activate transcription. To dissect the precise role of nuclear factor 1 (NF1) in chromatin remodeling and transcriptional activation, we used linker-scanning mutants of transcription factor binding sites on the MMTV promoter. We compared the NF1 mutant MMTV promoter in the context of transiently transfected templates (transient transfection) and templates organized as chromatin (stable transfection) to understand the effect of chromatin on factor binding and transcription. We show that on a transiently transfected template, mutation in the NF1 binding site reduces both basal and hormone-dependent transcription. This suggests that NF1 is required for transcription in the absence of organized chromatin. We also found that binding of NF1 on a transiently transfected template is independent of mutation in hormone response elements or the octamer transcription factor (OTF) binding site. In contrast, the binding of OTF proteins to a transiently transfected template was found to be dependent on the binding of NF1, which may imply that NF1 has a stabilizing effect on OTF binding. On a chromatin template, mutation in the NF1 binding site does not affect the positioning of nucleosomes on the promoter. We also show that in the absence of NF1 binding, GR-mediated chromatin remodeling of nucleosome B is reduced and hormone-dependent activation of transcription is abolished. Further, we demonstrate that NF1 is required for both the association of BRG1 chromatin remodeling complex and the GR on the promoter in vivo. These results suggest the novel possibility that NF1 may participate in chromatin remodeling activities in addition to directly enhancing transcription and that in the absence of its binding site the GR is unable to effectively bind the promoter and recruit the remodeling complex.