Correlating Transcription Initiation and Conformational Changes by a Single-Subunit RNA Polymerase with Near Base-Pair Resolution

Mol Cell. 2018 May 17;70(4):695-706.e5. doi: 10.1016/j.molcel.2018.04.018.


We provide a comprehensive analysis of transcription in real time by T7 RNA Polymerase (RNAP) using single-molecule fluorescence resonance energy transfer by monitoring the entire life history of transcription initiation, including stepwise RNA synthesis with near base-pair resolution, abortive cycling, and transition into elongation. Kinetically branching pathways were observed for abortive initiation with an RNAP either recycling on the same promoter or exchanging with another RNAP from solution. We detected fast and slow populations of RNAP in their transition into elongation, consistent with the efficient and delayed promoter release, respectively, observed in ensemble studies. Real-time monitoring of abortive cycling using three-probe analysis showed that the initiation events are stochastically branched into productive and failed transcription. The abortive products are generated primarily from initiation events that fail to progress to elongation, and a majority of the productive events transit to elongation without making abortive products.

Keywords: FRET; T7 RNA polymerase; abortive RNA; closed complex; fluorescence; open complex; promoter DNA; single-molecule; transcription initiation; transition to elongation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA-Directed RNA Polymerases / chemistry*
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism*
  • Humans
  • Promoter Regions, Genetic*
  • Protein Binding
  • Protein Subunits
  • RNA / chemistry*
  • RNA / genetics
  • RNA / metabolism
  • Transcription Initiation Site*
  • Transcription, Genetic*
  • Viral Proteins / chemistry*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*


  • Protein Subunits
  • Viral Proteins
  • RNA
  • bacteriophage T7 RNA polymerase
  • DNA-Directed RNA Polymerases