Coupling transcription and translation In bacteria, the transcription of DNA into mRNA by RNA polymerase is coupled to the translation of that mRNA into protein by the ribosome. How this coupling is achieved has been unclear. Kohler et al. show that RNA polymerase and the ribosome from Escherichia coli can form a so-called expressome complex. Electron microscopy structural analysis, together with functional experiments, revealed details of the coupled complex. The coupling could allow translation to prevent transcriptional pausing, backtracking, and termination. Science, this issue p. 194 The structure of an RNA polymerase–ribosome complex suggests the molecular basis for transcription-translation coupling. DNA transcription is functionally coupled to messenger RNA (mRNA) translation in bacteria, but how this is achieved remains unclear. Here we show that RNA polymerase (RNAP) and the ribosome of Escherichia coli can form a defined transcribing and translating “expressome” complex. The cryo–electron microscopic structure of the expressome reveals continuous protection of ~30 nucleotides of mRNA extending from the RNAP active center to the ribosome decoding center. The RNAP-ribosome interface includes the RNAP subunit α carboxyl-terminal domain, which is required for RNAP-ribosome interaction in vitro and for pronounced cell growth defects upon translation inhibition in vivo, consistent with its function in transcription-translation coupling. The expressome structure can only form during transcription elongation and explains how translation can prevent transcriptional pausing, backtracking, and termination.

中文翻译：

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转录-翻译表达组的架构

转录和翻译的偶联 在细菌中，RNA 聚合酶将 DNA 转录为 mRNA 与核糖体将 mRNA 翻译为蛋白质的过程偶联。这种耦合是如何实现的还不清楚。科勒等人。表明 RNA 聚合酶和来自大肠杆菌的核糖体可以形成所谓的表达组复合体。电子显微镜结构分析以及功能实验揭示了耦合复合物的细节。这种耦合可以允许翻译防止转录暂停、回溯和终止。科学，这个问题 p。194 RNA 聚合酶-核糖体复合物的结构暗示了转录-翻译偶联的分子基础。DNA 转录在功能上与细菌中的信使 RNA (mRNA) 翻译耦合，但如何实现这一点仍不清楚。在这里，我们表明 RNA 聚合酶 (RNAP) 和大肠杆菌的核糖体可以形成一个明确的转录和翻译“表达组”复合体。表达组的冷冻电子显微结构揭示了从 RNAP 活性中心延伸到核糖体解码中心的约 30 个 mRNA 核苷酸的持续保护。RNAP-核糖体界面包括 RNAP 亚基 α 羧基末端结构域，这是体外 RNAP-核糖体相互作用和体内翻译抑制后明显细胞生长缺陷所必需的，与其在转录-翻译偶联中的功能一致。表达组结构只能在转录延伸过程中形成，并解释了翻译如何防止转录暂停、回溯和终止。