PHOX2B regulates its own expression by a transcriptional auto-regulatory mechanism
PHOX2B regulates its own expression by a transcriptional auto-regulatory mechanism
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DOI：
10.1074/jbc.m508368200
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发表时间：
2005-11-11
影响因子：
4.8
通讯作者：
Fornasari, D
中科院分区：
文献类型：
--
作者：
Cargnin, F;Flora, A;Fornasari, D
神经元身份的规范是以下两种不同类别的决定因素之间的相互作用的结果：外在因素，包括分泌或细胞膜相关的信号在当地的环境，和内在因素，通常由有序级联的转录因子。关于这些外在和内在因素之间相互作用的分子机制以及建立和维持给定神经元表型的转录过程知之甚少。Phox2b是一种脊椎动物同源结构域转录因子，是发育自主神经节的一种成熟的内在因子，其表达由背主动脉分泌的骨形态发生蛋白触发。在这项研究中，我们表征了它的近端5 '调控区，发现它含有五个推定的DNA位点，可能结合同源结构域蛋白，包括PHOX 2B本身。染色质免疫沉淀试验表明PHOX 2B在体内可以结合其自身的启动子，电迁移率凝胶迁移试验证实，5个位点中的4个可能参与PHOX 2B结合。功能实验表明，在神经母细胞瘤细胞中PHOX 2B启动子的转录活性的65%取决于这种自动调节机制，并且所有四个位点都是完全自我反式激活所需的。我们的数据提供了一个可能的分子解释PHOX2B表达的维护在发展中的神经节，其中最初它的表达是由骨形态发生蛋白触发，但可能成为独立的外部刺激时，它达到一定的核浓度，并维持自己的转录。
The specification of neuronal identity is a result of interactions between the following two distinct classes of determinants: extrinsic factors that include secreted or cell membrane-associated signals in the local environment, and intrinsic factors that generally consist of ordered cascades of transcription factors. Little is known about the molecular mechanisms underlying the interplay between these extrinsic and intrinsic factors and the transcriptional processes that establish and maintain a given neuronal phenotype. Phox2b is a vertebrate homeodomain transcription factor and a well established intrinsic factor in developing autonomic ganglia, where its expression is triggered by the bone morphogenic proteins secreted by the dorsal aorta. In this study we characterized its proximal 5'-regulatory region and found that it contained five putative DNA sites that potentially bind homeodomain proteins, including PHOX2B itself. Chromatin immunoprecipitation assays showed that PHOX2B could bind its own promoter in vivo, and electromobility gel shift assays confirmed that four of the five sites could be involved in PHOX2B binding. Functional experiments demonstrated that 65% of the transcriptional activity of the PHOX2B promoter in neuroblastoma cells depends on this auto-regulatory mechanism and that all four sites were required for full self-transactivation. Our data provide a possible molecular explanation for the maintenance of PHOX2B expression in developing ganglia, in which initially its expression is triggered by bone morphogenic proteins, but may become independent of external stimuli when it reaches a certain nuclear concentration and sustains its own transcription.