Measures of single- versus multiple-round translation argue against a mechanism to ensure coupling of transcription and translation
Measures of single- versus multiple-round translation argue against a mechanism to ensure coupling of transcription and translation
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DOI：
10.1073/pnas.1812940115
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发表时间：
2018-10-16
影响因子：
11.1
通讯作者：
Fredrick, Kurt
中科院分区：
文献类型：
--
作者：
Chen, Menglin;Fredrick, Kurt
在原核生物中，RNA和蛋白质的合成同时发生在细胞质中。许多研究表明，翻译可以强烈影响转录，这种现象通常归因于RNA聚合酶（RNAP）和新生mRNA上的前导核糖体之间的物理偶联。是否普遍存在确保或促进RNAP-核糖体偶联的机制仍不清楚。在这里，我们使用了一种有效的锤头状核酶，并开发了一个报告系统，以衡量单轮与多轮翻译大肠杆菌。分析了六对共转录和差异翻译的基因。对于其中的五个，当野生型细胞中翻译的轮次严重减少时，两种蛋白质产物的化学计量比并没有接近统一（1：1）。引入突变rpoB（I572 N），其减慢RNAP延伸，可以促进偶联，如单轮测定中化学计量的SspA和SspB产物所示。这些数据是一致的随机耦合模型，其中耦合的概率取决于转录和翻译的相对速率，并表明RNAP经常转录没有一个连接的核糖体。
In prokaryotes, the synthesis of RNA and protein occurs simultaneously in the cytoplasm. A number of studies indicate that translation can strongly impact transcription, a phenomenon often attributed to physical coupling between RNA polymerase (RNAP) and the lead ribosome on the nascent mRNA. Whether there generally exists a mechanism to ensure or promote RNAP-ribosome coupling remains unclear. Here, we used an efficient hammerhead ribozyme and developed a reporter system to measure single- versus multiple-round translation in Escherichia coli. Six pairs of cotranscribed and differentially translated genes were analyzed. For five of them, the stoichiometry of the two protein products came no closer to unity (1:1) when the rounds of translation were severely reduced in wild-type cells. Introduction of mutation rpoB(I572N), which slows RNAP elongation, could promote coupling, as indicated by stoichiometric SspA and SspB products in the single-round assay. These data are consistent with models of stochastic coupling in which the probability of coupling depends on the relative rates of transcription and translation and suggest that RNAP often transcribes without a linked ribosome.