文章基本信息

标题：Trigger loop dynamics mediate the balance between the transcriptional fidelity and speed of RNA polymerase II
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作者：Matthew H. Larson ; Jing Zhou ; Craig D. Kaplan 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2012
卷号：109
期号：17
页码：6555-6560
DOI：10.1073/pnas.1200939109
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：During transcription, RNA polymerase II (RNAPII) must select the correct nucleotide, catalyze its addition to the growing RNA transcript, and move stepwise along the DNA until a gene is fully transcribed. In all kingdoms of life, transcription must be finely tuned to ensure an appropriate balance between fidelity and speed. Here, we used an optical-trapping assay with high spatiotemporal resolution to probe directly the motion of individual RNAPII molecules as they pass through each of the enzymatic steps of transcript elongation. We report direct evidence that the RNAPII trigger loop, an evolutionarily conserved protein subdomain, serves as a master regulator of transcription, affecting each of the three main phases of elongation, namely: substrate selection, translocation, and catalysis. Global fits to the force-velocity relationships of RNAPII and its trigger loop mutants support a Brownian ratchet model for elongation, where the incoming NTP is able to bind in either the pre- or posttranslocated state, and movement between these two states is governed by the trigger loop. Comparison of the kinetics of pausing by WT and mutant RNAPII under conditions that promote base misincorporation indicate that the trigger loop governs fidelity in substrate selection and mismatch recognition, and thereby controls aspects of both transcriptional accuracy and rate.
关键词：optical trap ; optical tweezers ; Pol II