title: Conserved functions of the trigger loop and Gre factors in RNA cleavage by bacterial RNA polymerases.
abstract: RNA cleavage by RNA polymerase (RNAP) is the central step in co-transcriptional RNA proofreading. Bacterial RNAPs were proposed to rely on the same mobile element of the active site, the trigger loop (TL), for both nucleotide addition and RNA cleavage. RNA cleavage can also be stimulated by universal Gre factors, which should replace the TL to get access to the RNAP active site. The contributions of the TL and Gre factors to RNA cleavage reportedly vary between RNAPs from different bacterial species and, probably, different types of transcription complexes. Here, by comparing RNAPs fromEscherichia coli,Deinococcus radiodurans, andThermus aquaticus, we show that the functions of the TL and Gre factors in RNA cleavage are conserved in various species, with important variations that may be related to extremophilic adaptation. Deletions of the TL strongly impair intrinsic RNA cleavage by all three RNAPs and eliminate the interspecies differences in the reaction rates. GreA factors activate RNA cleavage by wild-type RNAPs to similar levels. The rates of GreA-dependent cleavage are lower for ΔTL RNAP variants, suggesting that the TL contributes to the Gre function. Finally, neither the TL nor GreA can efficiently activate RNA cleavage in certain types of backtracked transcription complexes, suggesting that these complexes adopt a catalytically inactive conformation probably important for transcription regulation.
authors.affiliation: From the Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Miropolskaya
authors.affiliation: From the Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia.
authors.forename: Daria
authors.initials: D
authors.lastname: Esyunina
authors.affiliation: From the Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia akulb@img.ras.ru.
authors.forename: Andrey
authors.identifier: 0000-0002-2292-6424
authors.initials: A
authors.lastname: Kulbachinskiy
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000737:chemistry*; D034301:Deinococcus / Q000201:enzymology*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry; D017353:Gene Deletion; D014644:Genetic Variation; D012313:RNA / Q000737:chemistry*; D059367:RNA Cleavage; D013824:Thermus / Q000201:enzymology*; D014157:Transcription Factors / Q000737:chemistry; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; C079668:GreA protein, E coli; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D012313:RNA; D012321:DNA-Directed RNA Polymerases
keywords: GreA; RNA metabolism; RNA polymerase; RNA proofreading; bacterial transcription; gene expression; transcription elongation complex; transcription elongation factor