Blombach Fabian, Smollett Katherine L, Grohmann Dina, Werner Finn
Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, UK.
Institute of Microbiology, University of Regensburg, Regensburg 93053, Germany.
J Mol Biol. 2016 Jun 19;428(12):2592-2606. doi: 10.1016/j.jmb.2016.04.016. Epub 2016 Apr 20.
Transcription initiation requires that the promoter DNA is melted and the template strand is loaded into the active site of the RNA polymerase (RNAP), forming the open complex (OC). The archaeal initiation factor TFE and its eukaryotic counterpart TFIIE facilitate this process. Recent structural and biophysical studies have revealed the position of TFE/TFIIE within the pre-initiation complex (PIC) and illuminated its role in OC formation. TFE operates via allosteric and direct mechanisms. Firstly, it interacts with the RNAP and induces the opening of the flexible RNAP clamp domain, concomitant with DNA melting and template loading. Secondly, TFE binds physically to single-stranded DNA in the transcription bubble of the OC and increases its stability. The identification of the β-subunit of archaeal TFE enabled us to reconstruct the evolutionary history of TFE/TFIIE-like factors, which is characterised by winged helix (WH) domain expansion in eukaryotes and loss of metal centres including iron-sulfur clusters and Zinc ribbons. OC formation is an important target for the regulation of transcription in all domains of life. We propose that TFE and the bacterial general transcription factor CarD, although structurally and evolutionary unrelated, show interesting parallels in their mechanism to enhance OC formation. We argue that OC formation is used as a way to regulate transcription in all domains of life, and these regulatory mechanisms coevolved with the basal transcription machinery.
转录起始需要启动子DNA解链，模板链加载到RNA聚合酶（RNAP）的活性位点，形成开放复合物（OC）。古菌起始因子TFE及其真核对应物TFIIE促进这一过程。最近的结构和生物物理研究揭示了TFE/TFIIE在起始前复合物（PIC）中的位置，并阐明了其在OC形成中的作用。TFE通过变构和直接机制发挥作用。首先，它与RNAP相互作用，诱导柔性RNAP钳结构域打开，同时伴随DNA解链和模板加载。其次，TFE与OC转录泡中的单链DNA物理结合，增加其稳定性。古菌TFE的β亚基的鉴定使我们能够重建TFE/TFIIE样因子的进化历史，其特征是真核生物中有翼螺旋（WH）结构域扩展，以及包括铁硫簇和锌带在内的金属中心丢失。OC形成是生命所有领域转录调控的一个重要靶点。我们提出，TFE和细菌通用转录因子CarD虽然在结构和进化上不相关，但在增强OC形成的机制上显示出有趣的相似之处。我们认为，OC形成被用作生命所有领域调节转录的一种方式，并且这些调节机制与基础转录机制共同进化。
