Release of Human TFIIB from Actively Transcribing Complexes Is Triggered upon Synthesis of 7- and 9-nt RNAs
Release of Human TFIIB from Actively Transcribing Complexes Is Triggered upon Synthesis of 7- and 9-nt RNAs
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7-nt 和 9-nt RNA 合成后触发人 TFIIB 从主动转录复合物中释放
DOI：
10.1016/j.jmb.2020.05.005
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发表时间：
2020
影响因子：
5.6
通讯作者：
Kugel, Jennifer F.
中科院分区：
文献类型：
--
作者：
Ly, Elina;Powell, Abigail E.;Goodrich, James A.;Kugel, Jennifer F.
RNA 聚合酶 II (Pol II) 及其通用转录因子在 mRNA 基因的启动子上组装，形成大的大分子复合物，以受调控的方式启动转录。在早期转录过程中，随着 Pol II 远离转录起始位点并转变为延伸，这些复合物会经历动态重排和分解。分解的一个步骤是通用转录因子 TFIIB 的释放，尽管释放机制及其与转录 Pol II 活性的关系尚不清楚。我们开发了单分子荧光转录系统来研究 TFIIB 的体外释放。利用我们区分活性复合物和非活性复合物的能力，我们发现几乎所有转录活性复合物在早期转录过程中都会释放 TFIIB。释放不依赖于 TFIIB 与其启动子 DNA 中的识别元件的接触。我们确定了早期转录中触发释放的两个不同点，反映了活跃转录复合物群体的异质性。 TFIIB 在两个触发点后以相似的动力学释放，表明释放速率与促进释放的分子转化无关。我们的数据共同支持了这样的模型：随着起始复合物转变为延伸复合物，TFIIB 的释放对于 Pol II 成功逃离启动子非常重要。
RNA polymerase II (Pol II) and its general transcription factors assemble on the promoters of mRNA genes to form large macromolecular complexes that initiate transcription in a regulated manner. During early transcription, these complexes undergo dynamic rearrangement and disassembly as Pol II moves away from the start site of transcription and transitions into elongation. One step in disassembly is the release of the general transcription factor TFIIB, although the mechanism of release and its relationship to the activity of transcribing Pol II is not understood. We developed a single-molecule fluorescence transcription system to investigate TFIIB releasein vitro. Leveraging our ability to distinguish active from inactive complexes, we found that nearly all transcriptionally active complexes release TFIIB during early transcription. Release is not dependent on the contacts TFIIB makes with its recognition element in promoter DNA. We identified two different points in early transcription at which release is triggered, reflecting heterogeneity across the population of actively transcribing complexes. TFIIB releases after both trigger points with similar kinetics, suggesting the rate of release is independent of the molecular transformations that prompt release. Together our data support the model that TFIIB release is important for Pol II to successfully escape the promoter as initiating complexes transition into elongation complexes.