Structural and mechanistic basis of reiterative transcription initiation

Autor: Richard H. Ebright, Chirangini Pukhrambam, Jason T. Kaelber, Jared T. Winkelman, Bryce E. Nickels, Emre Firlar, Yu Liu, Yu Zhang, Libing Yu
Rok vydání: 2021
Předmět:
Zdroj: Proceedings of the National Academy of Sciences of the United States of America. 119(5)
ISSN: 1091-6490
Popis: Reiterative transcription initiation, observed at promoters that contain homopolymeric sequences at the transcription start site, generates RNA products having 5’ sequences non-complementary to the DNA template. Here, using crystallography and cryo-EM 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 RNAP-dependent DNA unwinding, we show that RNA extension in reiterative transcription initiation: (1) occurs without DNA scrunching, (2) involves a short, 2-3 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.
Databáze: OpenAIRE