Structural basis of reiterative transcription from the pyrG and pyrBI promoters by bacterial RNA polymerase [article]

Yeonoh Shin, Mark Hedglin, Katsuhiko Murakami
2019 bioRxiv   pre-print
Reiterative transcription is a non-canonical form of RNA synthesis by RNA polymerase in which a ribonucleotide specified by a single base in the DNA template is repetitively added to the nascent RNA transcript. We previously determined the X-ray crystal structure of the bacterial RNA polymerase engaged in reiterative transcription from the pyrG promoter, which contains 8 poly-G RNA bases synthesized using 3 C bases in the DNA as a template and extends RNA without displacement of the promoter
more » ... ognition σ factor from the core enzyme. In this study, we determined a series of transcript initiation complex structures from the pyrG promoter using soak trigger freeze X-ray crystallography. We also performed biochemical assays to monitor template DNA translocation during RNA synthesis from the pyrG promoter and in vitro transcription assays to determine the length of poly-G RNA from the pyrG promoter variants. Structures and biochemical assays revealed how the RNA transcript from the pyrG promoter is guided toward the Rifampin-binding pocket then the main channel of RNA polymerase and provided insight into RNA slippage during reiterative transcription of the pyrG promoter. Lastly, we determined a structure of a reiterative transcription complex at the pyrBI promoter and revealed an alternative mechanism of RNA slippage and extension requiring the σ dissociation from the core enzyme.
doi:10.1101/732214 fatcat:76afmwk2mbgyvaq3gszhq7anbi