近日，复旦大学徐彦辉团队揭示转录启动过程中的结构可视化。该研究于2023年12月22日发表于国际一流学术期刊《科学》。

研究人员测定了新生RNA长度达到2至17个核苷酸时，RNA聚合酶II在无G启动子上停止的新生转录复合物TC2至TC17的结构。将这些结构连接起来，就生成了一部电影和一个工作模型。随着最初合成的RNA的增长，一般转录因子（GTF）仍与启动子结合，转录泡扩大。三磷酸核苷（NTP）驱动的RNA-DNA易位和模板链在几乎密封的通道中的积累可能会促进初始转录复合物（ITC，TC2至TC9）向早期延伸复合物（EEC，TC10至TC17）的过渡。

这项研究显示了转录起始的动态过程，并揭示了为什么ITC需要GTF和转录泡扩张来进行初始RNA合成，而EEC则需要GTF从启动子解离和转录泡塌陷来实现启动子逃逸。

据了解，转录起始是一个复杂的过程，其机制尚不完全清楚。

附：英文原文

Title: Structural visualization of transcription initiation in action

Author: Xizi Chen, Weida Liu, Qianmin Wang, Xinxin Wang, Yulei Ren, Xuechun Qu, Wanjun Li, Yanhui Xu

Issue&Volume: 2023-12-22

Abstract: Transcription initiation is a complex process, and its mechanism is incompletely understood. We determined the structures of de novo transcribing complexes TC2 to TC17 with RNA polymerase II halted on G-less promoters when nascent RNAs reach 2 to 17 nucleotides in length, respectively. Connecting these structures generated a movie and a working model. As initially synthesized RNA grows, general transcription factors (GTFs) remain bound to the promoter and the transcription bubble expands. Nucleoside triphosphate (NTP)–driven RNA-DNA translocation and template-strand accumulation in a nearly sealed channel may promote the transition from initially transcribing complexes (ITCs) (TC2 to TC9) to early elongation complexes (EECs) (TC10 to TC17). Our study shows dynamic processes of transcription initiation and reveals why ITCs require GTFs and bubble expansion for initial RNA synthesis, whereas EECs need GTF dissociation from the promoter and bubble collapse for promoter escape.

DOI: adi5120

Source: https://www.science.org/doi/10.1126/science.adi5120