Dual role of the nucleolar transcription factor UBF: trans-activator and antirepressor.
Dual role of the nucleolar transcription factor UBF: trans-activator and antirepressor.
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DOI：
10.1073/pnas.89.16.7340
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发表时间：
1992-08
影响因子：
11.1
通讯作者：
A. Kuhn;I. Grummt
中科院分区：
文献类型：
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作者：
A. Kuhn;I. Grummt
在由部分纯化的RNA聚合酶I （pol I）和起始因子tifi - ia、tifi - ib和tifi - ic组成的重组系统中，核核因子UBF（上游结合因子）刺激rrna编码DNA （rDNA）启动子的转录至少50倍。这种激活在高模板浓度或高纯度pol的存在下没有观察到。模板承诺实验表明，UBF通过缓解聚合酶部分中的负作用因子(s)施加的抑制来激活转录，该聚合酶部分竞争tiff - ib与rDNA启动子的结合，并阻止预起始复合物的形成。我们使用与DNA结合的纯化组蛋白H1作为rDNA启动子抑制状态的模型，表明UBF抵消了H1介导的pol I转录抑制。这些发现的意义讨论了蛋白质-蛋白质和蛋白质- dna在rDNA启动子上的相互作用，以及UBF可能参与控制核糖体基因转录。
In a reconstituted system consisting of partially purified RNA polymerase I (pol I) and the initiation factors TIF-IA, TIF-IB, and TIF-IC, the nucleolar factor UBF (upstream binding factor) stimulates transcription from the rRNA-encoding DNA (rDNA) promoter at least 50-fold. This activation is not observed at high template concentrations or in the presence of highly purified pol I. Template commitment experiments suggest that UBF activates transcription by relieving inhibition exerted by a negative-acting factor(s) in the polymerase fraction that competes for TIF-IB binding to the rDNA promoter and prevents the formation of preinitiation complexes. Using purified histone H1 bound to DNA as a model for the repressed state of the rDNA promoter, we show that UBF counteracts H1-mediated repression of pol I transcription. The implications of these findings are discussed with respect to the protein-protein and protein-DNA interactions at the rDNA promoter and the possible involvement of UBF in control of ribosomal gene transcription.