Conserved functions of the trigger loop and Gre factors in RNA cleavage by bacterial RNA polymerases.
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 from Escherichia coli, Deinococcus radiodurans, and Thermus 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.
['Miropolskaya|Nataliya|N|', 'Esyunina|Daria|D|', 'Kulbachinskiy|Andrey|A|0000-0002-2292-6424']
D012321:DNA-Directed RNA Polymerases D034301:Deinococcus D004926:Escherichia coli D029968:Escherichia coli Proteins D017353:Gene Deletion D014644:Genetic Variation D012313:RNA D059367:RNA Cleavage D013824:Thermus D014157:Transcription Factors D014158:Transcription, Genetic D035602:Transcriptional Elongation Factors
RNA polymerase RNA proofreading GreA RNA metabolism bacterial transcription gene expression transcription elongation complex transcription elongation factor