High intrinsic hydrolytic activity of cyanobacterial RNA polymerase compensates for the absence of transcription proofreading factors

Amber Riaz-Bradley, Katherine James, Yulia Yuzenkova

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
12 Downloads (Pure)

Abstract

The vast majority of organisms possess transcription elongation factors, the functionally similar bacterial Gre and eukaryotic/archaeal TFIIS/TFS. Their main cellular functions are to proofread errors of transcription and to restart elongation via stimulation of RNA hydrolysis by the active centre of RNA polymerase (RNAP). However, a number of taxons lack these factors, including one of the largest and most ubiquitous groups of bacteria, cyanobacteria. Using cyanobacterial RNAP as a model, we investigated alternative mechanisms for maintaining a high fidelity of transcription and for RNAP arrest prevention. We found that this RNAP has very high intrinsic proofreading activity, resulting in nearly as low a level of in vivo mistakes in RNA as Escherichia coli. Features of the cyanobacterial RNAP hydrolysis are reminiscent of the Gre-assisted reaction—the energetic barrier is similarly low, and the reaction involves water activation by a general base. This RNAP is resistant to ubiquitous and most regulatory pausing signals, decreasing the probability to go off-pathway and thus fall into arrest. We suggest that cyanobacterial RNAP has a specific Trigger Loop domain conformation, and isomerises easier into a hydrolytically proficient state, possibly aided by the RNA 3′-end. Cyanobacteria likely passed these features of transcription to their evolutionary descendants, chloroplasts.
Original languageEnglish
Pages (from-to)1341–1352
Number of pages12
JournalNucleic Acids Research
Volume48
Issue number3
Early online date16 Dec 2019
DOIs
Publication statusPublished - 20 Feb 2020

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