Structural and mechanistic basis of reiterative transcription initiation

Yu Liu, Libing Yu, Chirangini Pukhrambam, Jared T. Winkelman, Emre Firlar, Jason T. Kaelber, Yu Zhang, Bryce E. Nickels, Richard H. Ebright

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Reiterative transcription initiation, observed at promoters that contain homopolymeric sequences at the transcription start site, generates RNA products having 5 sequences noncomplementary to the DNA template. Here, using crystallography and cryoelectron microscopy to define structures, protein-DNA photocrosslinking to map positions of RNAP leading and trailing edges relative to DNA, and single-molecule DNA nanomanipulation to assess RNA polymerase (RNAP)-dependent DNA unwinding, we show that RNA extension in reiterative transcription initiation 1) occurs without DNA scrunching; 2) involves a short, 2- to 3-bp, RNA-DNA hybrid; and 3) generates RNA that exits RNAP through the portal by which scrunched nontemplate-strand DNA exits RNAP in standard transcription initiation. The results establish that, whereas RNA extension in standard transcription initiation proceeds through a scrunching mechanism, RNA extension in reiterative transcription initiation proceeds through a slippage mechanism, with slipping of RNA relative to DNA within a short RNA-DNA hybrid, and with extrusion of RNA from RNAP through an alternative RNA exit.

Original languageEnglish (US)
Article numbere2115746119
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - Feb 1 2022

All Science Journal Classification (ASJC) codes

  • General


  • DNA scrunching
  • RNA polymerase
  • Reiterative transcription initiation
  • Transcription
  • Transcriptional slippage


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