Steuten Benedikt, Hoch Philipp G, Damm Katrin, Schneider Sabine, Köhler Karen, Wagner Rolf, Hartmann Roland K
Heinrich-Heine-Universität Düsseldorf; Institut für Physikalische Biologie Universitätsstr; Düsseldorf, Germany.
Philipps-Universität Marburg; Marburg, Germany.
RNA Biol. 2014;11(5):508-21. doi: 10.4161/rna.28827. Epub 2014 Apr 23.
Whereas, the majority of bacterial non-coding RNAs and functional RNA elements regulate post-transcriptional processes, either by interacting with other RNAs via base-pairing or through binding of small ligands (riboswitches), 6S RNAs affect transcription itself by binding to the housekeeping holoenzyme of RNA polymerase (RNAP). Remarkably, 6S RNAs serve as RNA templates for bacterial RNAP, giving rise to the de novo synthesis of short transcripts, termed pRNAs (product RNAs). Hence, 6S RNAs prompt the enzyme to act as an RNA-dependent RNA polymerase (RdRP). Synthesis of pRNAs exceeding a certain length limit (~13 nt) persistently rearrange the 6S RNA structure, which in turn, disrupts the 6S RNA:RNAP complex. This pRNA synthesis-mediated "reanimation" of sequestered RNAP molecules represents the conceivably fastest mechanism for resuming transcription in cells that enter a new exponential growth phase. The many different 6S RNAs found in a wide variety of bacteria do not share strong sequence homology but have in common a conserved rod-shaped structure with a large internal loop, termed the central bulge; this architecture mediates specific binding to the active site of RNAP. In this article, we summarize the overall state of knowledge as well as very recent findings on the structure, function, and physiological effects of 6S RNA examples from the two model organisms, Escherichia coli and Bacillus subtilis. Comparison of the presently known properties of 6S RNAs in the two organisms highlights common principles as well as diverse features.
虽然大多数细菌非编码RNA和功能性RNA元件通过碱基配对与其他RNA相互作用或通过结合小配体（核糖开关）来调节转录后过程，但6S RNA通过与RNA聚合酶（RNAP）的管家全酶结合来影响转录本身。值得注意的是，6S RNA作为细菌RNAP的RNA模板，导致短转录本的从头合成，称为pRNA（产物RNA）。因此，6S RNA促使该酶充当RNA依赖性RNA聚合酶（RdRP）。超过一定长度限制（约13个核苷酸）的pRNA合成会持续重排6S RNA结构，进而破坏6S RNA：RNAP复合物。这种由pRNA合成介导的对被隔离的RNAP分子的“复活”代表了在进入新的指数生长期的细胞中恢复转录的可能最快机制。在各种各样的细菌中发现的许多不同的6S RNA没有很强的序列同源性，但共同具有一个保守的杆状结构，带有一个大的内部环，称为中央凸起；这种结构介导与RNAP活性位点的特异性结合。在本文中，我们总结了来自两种模式生物大肠杆菌和枯草芽孢杆菌的6S RNA的结构、功能和生理效应的总体知识状态以及最新发现。对这两种生物中目前已知的6S RNA特性的比较突出了共同原则以及不同特征。
