Structural basis for transcription activation Bacteria can initiate transcription through two independent classes of recruitment mechanisms. Liu et al. determined the cryo-electron microscopy structure of an intact class I transcription activation complex. The positions and orientations of all the components and the detailed protein-protein and protein-nucleic acid interactions reveal how an activator interacts with the promoter DNA and recruits RNA polymerase through the class I mechanism. Together with a recently reported class II transcription activation complex, the findings complete our structural understanding of bacterial transcription activation. Science, this issue p. 947 The cryo–electron microscopy structure of a bacterial transcription activation complex reveals how transcription is initiated. In bacteria, the activation of gene transcription at many promoters is simple and only involves a single activator. The cyclic adenosine 3′,5′-monophosphate receptor protein (CAP), a classic activator, is able to activate transcription independently through two different mechanisms. Understanding the class I mechanism requires an intact transcription activation complex (TAC) structure at a high resolution. Here we report a high-resolution cryo–electron microscopy structure of an intact Escherichia coli class I TAC containing a CAP dimer, a σ70–RNA polymerase (RNAP) holoenzyme, a complete class I CAP-dependent promoter DNA, and a de novo synthesized RNA oligonucleotide. The structure shows how CAP wraps the upstream DNA and how the interactions recruit RNAP. Our study provides a structural basis for understanding how activators activate transcription through the class I recruitment mechanism.

中文翻译：

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细菌转录激活的结构基础

转录激活的结构基础细菌可以通过两类独立的募集机制启动转录。刘等人。确定了完整的 I 类转录激活复合物的冷冻电子显微镜结构。所有组件的位置和方向以及详细的蛋白质-蛋白质和蛋白质-核酸相互作用揭示了激活剂如何与启动子 DNA 相互作用并通过 I 类机制招募 RNA 聚合酶。连同最近报道的 II 类转录激活复合物，这些发现完成了我们对细菌转录激活的结构理解。科学，这个问题 p。947 细菌转录激活复合物的低温电子显微镜结构揭示了转录是如何启动的。在细菌中，在许多启动子上激活基因转录很简单，只涉及一个激活子。环状腺苷 3',5'-单磷酸受体蛋白 (CAP) 是一种经典的激活剂，能够通过两种不同的机制独立激活转录。了解 I 类机制需要高分辨率的完整转录激活复合物 (TAC) 结构。在这里，我们报告了包含 CAP 二聚体、σ70-RNA 聚合酶 (RNAP) 全酶、完整的 I 类 CAP 依赖性启动子 DNA 和从头合成的完整大肠杆菌 I 类 TAC 的高分辨率冷冻电子显微镜结构RNA寡核苷酸。该结构显示了 CAP 如何包裹上游 DNA 以及相互作用如何招募 RNAP。