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Transcription elongation by RNA polymerase II (Pol II) is an integral step in eukaryotic gene expression. The speed of Pol II is controlled by a multitude of elongation factors, but the regulatory mechanisms remain incompletely understood, especially for higher eukaryotes. In this work, we developed a single-molecule platform to visualize the dynamics of in vitro reconstituted mammalian transcription elongation complexes (ECs). This platform enabled us to follow the elongation and pausing behavior of EC in real time and dissect the role of each elongation factor in the kinetic control of Pol II. We found that the mammalian EC harbors multiple gears depending on its associated factors and phosphorylation status. The elongation factors are not functionally redundant but act hierarchically and synergistically to achieve optimal EC activity. Such exquisite kinetic regulation may reflect the speed-changing events during the transcription cycle, such as pause-release and termination, and enable cells to adapt to a changing environment.

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RNA聚合酶II（Pol II）介导的转录延伸是真核生物基因表达中的关键步骤。虽然已有大量研究表明，Pol II的延伸速度受多种延伸因子的调控，但其具体的调控机制，尤其是在高等真核生物中的调控机制仍未完全被揭示。

本次线上直播讲座，我们有幸邀请到来自美国洛克菲勒大学刘诗欣组的王昱焜博士，分享其在单分子水平重建哺乳动物转录延伸复合物（EC）平台方面的突破性研究成果。该研究利用LUMICKS C-Trap实时观察EC的延伸与停顿过程，揭示各类延伸因子如何协同调控Pol II动力学状态，推动转录过程的精细调节。