Thiel G, Lietz M, Bach K, Guethlein L, Cibelli G
Department of Medical Biochemistry and Molecular Biology, University of Saarland Medical School, Homburg, Germany.
Biol Chem. 2001 Jun;382(6):891-902. doi: 10.1515/BC.2001.111.
Research on the regulation of transcription in mammals has focused in recent years mainly on the mechanism of transcriptional activation. However, transcriptional repression mediated by repressor proteins is a common regulatory mechanism in mammals and might play an important role in many biological processes. To understand the molecular mechanism of transcriptional repression, the activity of eight mammalian repressors or repressor domains was investigated using a set of model promoters in combination with two different transcriptional detection methods. The repressors studied were: REST, the thyroid hormone receptors alpha and beta, the zinc finger protein NK10 containing a 'krüppel-associated box' (KRAB), repressor domains derived from the proteins Egr-1, Oct2A and Dr1 and the repressor/activator protein YY1. Here we show that the repressor domains of REST, Egr-1, the thyroid hormone receptors alpha< and beta and NK10 were transferable to a heterologous DNA-binding domain and repressed transcription from proximal and distal positions. Moreover, these repressor domains also blocked the activity of a strong viral enhancer in a 'remote position'. Thus, these domains are 'general' transcriptional repressor domains. The 'krüppel-associated box' was the most powerful repressor domain tested. In contrast, the repressor domains derived from Oct2A and Dr1 were inactive when fused to a heterologous DNA-binding domain. The repressor domain of YY1 exhibited transcriptional repression activity only in one of the transcriptional assay systems. The recruitment of histone deacetylases to the proximity of the basal transcriptional apparatus was recently discussed as a mechanism for some mammalian transcriptional repressor proteins. Here we show here that histone deacetylase 2, targeted to the reporter gene via DNA-protein interaction, functions as a transcriptional repressor protein regardless of the location of its binding site within the transcription unit.
近年来，对哺乳动物转录调控的研究主要集中在转录激活机制上。然而，由阻遏蛋白介导的转录抑制是哺乳动物中一种常见的调控机制，可能在许多生物学过程中发挥重要作用。为了理解转录抑制的分子机制，我们使用一组模型启动子结合两种不同的转录检测方法，研究了8种哺乳动物阻遏蛋白或阻遏结构域的活性。所研究的阻遏蛋白包括：REST、甲状腺激素受体α和β、含有“克勒ppel相关盒”（KRAB）的锌指蛋白NK10、源自Egr-1、Oct2A和Dr1蛋白的阻遏结构域以及阻遏/激活蛋白YY1。我们在此表明，REST、Egr-1、甲状腺激素受体α和β以及NK10的阻遏结构域可转移至异源DNA结合结构域，并从近端和远端位置抑制转录。此外，这些阻遏结构域还能在“远距离位置”阻断强病毒增强子的活性。因此，这些结构域是“通用”的转录阻遏结构域。“克勒ppel相关盒”是所测试的最强大的阻遏结构域。相比之下，源自Oct2A和Dr1的阻遏结构域与异源DNA结合结构域融合时无活性。YY1的阻遏结构域仅在一种转录检测系统中表现出转录抑制活性。最近，有人讨论了组蛋白脱乙酰酶募集到基础转录装置附近作为某些哺乳动物转录阻遏蛋白的一种机制。我们在此表明，通过DNA-蛋白质相互作用靶向报告基因的组蛋白脱乙酰酶2，无论其结合位点在转录单元内的位置如何，都作为转录阻遏蛋白发挥作用。
