The interaction between σ70 and the β-flap of Escherichia coli RNA polymerase inhibits extension of nascent RNA during early elongation
The interaction between σ70 and the β-flap of Escherichia coli RNA polymerase inhibits extension of nascent RNA during early elongation
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DOI：
10.1073/pnas.0409850102
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发表时间：
2005-03-22
影响因子：
11.1
通讯作者：
Hochschild, A
中科院分区：
文献类型：
--
作者：
Nickels, BE;Garrity, SJ;Hochschild, A
细菌 RNA 聚合酶 (RNAP) 的 σ 亚基是启动子特异性转录起始所必需的。该功能取决于 sigma 与 RNAP 核心酶结合形成 RNAP 全酶时发生的特定亚基间相互作用。在这些相互作用中，sigma 的保守区 4 和 RNAP β 亚基的瓣结构域 (β-flap) 之间的相互作用对于识别主要类型的细菌启动子至关重要。在这里，我们描述了大肠杆菌 sigma(70) 区域 4 中氨基酸取代的分离，这些取代对 sigma(70) 区域 4/β-flap 相互作用具有特定影响，削弱或加强它。使用这些 sigma(70) 突变体，我们证明 sigma 区域 4/β-flap 相互作用也可以影响早期延伸过程中转录起始下游发生的事件。具体来说，我们的结果为基于结构的提议提供了支持，即当与 β-flap 结合时，sigma 区域 4 在新生 RNA 从 RNA 出口通道出现时对它的延伸形成障碍。我们的研究结果支持这样的观点，即从起始到延伸的转变涉及西格玛-核心相互作用的阶段性破坏。
The sigma-subunit of bacterial RNA polymerase (RNAP) is required for promoter-specific transcription initiation. This function depends on specific intersubunit interactions that occur when sigma associates with the RNAP core enzyme to form RNAP holoenzyme. Among these interactions, that between conserved region 4 of sigma and the flap domain of the RNAP beta-subunit (beta-flap) is critical for recognition of the major class of bacterial promoters. Here, we describe the isolation of amino acid substitutions in region 4 of Escherichia coli sigma(70) that have specific effects on the sigma(70) region 4/beta-flap interaction, either weakening or strengthening it. Using these sigma(70) mutants, we demonstrate that the sigma region 4/beta-flap interaction also can affect events occurring downstream of transcription initiation during early elongation. Specifically, our results provide support for a structure-based proposal that, when bound to the beta-flap, sigma region 4 presents a barrier to the extension of the nascent RNA as it emerges from the RNA exit channel. Our findings support the view that the transition from initiation to elongation involves a staged disruption of sigma-core interactions.