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首页> 美国卫生研究院文献>Journal of Bacteriology >Escherichia coli Promoters with UP Elements of Different Strengths: Modular Structure of Bacterial Promoters
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Escherichia coli Promoters with UP Elements of Different Strengths: Modular Structure of Bacterial Promoters

机译：具有不同强度的UP元素的大肠杆菌启动子：细菌启动子的模块化结构

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The α subunit of Escherichia coli RNA polymerase (RNAP) participates in promoter recognition through specific interactions with UP element DNA, a region upstream of the recognition hexamers for the ς subunit (the −10 and −35 hexamers). UP elements have been described in only a small number of promoters, including the rRNA promoter rrnB P1, where the sequence has a very large (30- to 70-fold) effect on promoter activity. Here, we analyzed the effects of upstream sequences from several additional E. coli promoters (rrnD P1, rrnB P2, λ pR, lac, merT, and RNA II). The relative effects of different upstream sequences were compared in the context of their own core promoters or as hybrids to the lac core promoter. Different upstream sequences had different effects, increasing transcription from 1.5- to ∼90-fold, and several had the properties of UP elements: they increased transcription in vitro in the absence of accessory protein factors, and transcription stimulation required the C-terminal domain of the RNAP α subunit. The effects of the upstream sequences correlated generally with their degree of similarity to an UP element consensus sequence derived previously. Protection of upstream sequences by RNAP in footprinting experiments occurred in all cases and was thus not a reliable indicator of UP element strength. These data support a modular view of bacterial promoters in which activity reflects the composite effects of RNAP interactions with appropriately spaced recognition elements (−10, −35, and UP elements), each of which contributes to activity depending on its similarity to the consensus.
机译：大肠杆菌RNA聚合酶（RNAP）的α亚基通过与UP元素DNA的特异性相互作用参与启动子的识别，UP元素DNA是ς亚基识别六聚体（-10和-35六聚体）上游的区域。仅在少数启动子中描述了UP元件，包括rRNA启动子rrnB P1，其中该序列对启动子活性的影响非常大（30到70倍）。在这里，我们分析了来自其他几个大肠杆菌启动子（rrnD P1，rrnB P2，λpR，lac，merT和RNA II）的上游序列的影响。在它们自己的核心启动子或与lac核心启动子杂交的情况下比较了不同上游序列的相对作用。不同的上游序列具有不同的作用，将转录从1.5倍增加到90倍左右，并且一些具有UP元件的特性：在没有辅助蛋白因子的情况下，它们在体外增加了转录，转录刺激需要C的C末端结构域RNAPα亚基。上游序列的作用通常与其与先前获得的UP元件共有序列的相似程度相关。在所有情况下，在足迹实验中都发生了由RNAP保护上游序列的情况，因此这并不是UP元素强度的可靠指标。这些数据支持细菌启动子的模块化视图，其中活性反映了RNAP与适当间隔的识别元件（-10，-35和UP元件）相互作用的复合作用，每个元件都取决于与共识的相似性而有助于活性。

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