Department of Biochemistry, University of Turku, Turku, Finland.
Department of Microbiology and The Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
J Mol Biol. 2019 Sep 20;431(20):3975-4006. doi: 10.1016/j.jmb.2019.05.042. Epub 2019 May 31.
Multi-subunit DNA-dependent RNA polymerases synthesize all classes of cellular RNAs, ranging from short regulatory transcripts to gigantic messenger RNAs. RNA polymerase has to make each RNA product in just one try, even if it takes millions of successive nucleotide addition steps. During each step, RNA polymerase selects a correct substrate, adds it to a growing chain, and moves one nucleotide forward before repeating the cycle. However, RNA synthesis is anything but monotonous: RNA polymerase frequently pauses upon encountering mechanical, chemical and torsional barriers, sometimes stepping back and cleaving off nucleotides from the growing RNA chain. A picture in which these intermittent dynamics enable processive, accurate, and controllable RNA synthesis is emerging from complementary structural, biochemical, computational, and single-molecule studies. Here, we summarize our current understanding of the mechanism and regulation of the on-pathway transcription elongation. We review the details of substrate selection, catalysis, proofreading, and translocation, focusing on rate-limiting steps, structural elements that modulate them, and accessory proteins that appear to control RNA polymerase translocation.
多亚基 DNA 依赖性 RNA 聚合酶合成所有类型的细胞 RNA，从短的调控转录物到巨大的信使 RNA。RNA 聚合酶必须在一次尝试中合成每种 RNA 产物，即使这需要数百万个连续的核苷酸添加步骤。在每个步骤中，RNA 聚合酶选择正确的底物，将其添加到正在生长的链中，并在重复循环之前向前移动一个核苷酸。然而，RNA 合成绝非单调乏味：RNA 聚合酶在遇到机械、化学和扭转障碍时经常会暂停，有时会后退并从正在生长的 RNA 链上切割核苷酸。互补的结构、生化、计算和单分子研究正在描绘出一幅图景，其中这些间歇性动力学使连续、准确和可控的 RNA 合成成为可能。在这里，我们总结了我们对转录延伸过程中机制和调节的理解。我们回顾了底物选择、催化、校对和易位的细节，重点关注限速步骤、调节它们的结构元件以及似乎控制 RNA 聚合酶易位的辅助蛋白。
