Structural basis of transcriptional pausing in bacteria.
Publication Type:Journal Article
Source:Cell, Volume 152, Issue 3, p.431-41 (2013)
Keywords:Catalytic Domain, Crystallography, X-Ray, DNA-Directed RNA Polymerases, Inverted Repeat Sequences, Nucleotides, RNA, Messenger, Thermus, Thermus thermophilus, Transcription Elongation, Genetic, Transcription Termination, Genetic
<p>Transcriptional pausing by multisubunit RNA polymerases (RNAPs) is a key mechanism for regulating gene expression in both prokaryotes and eukaryotes and is a prerequisite for transcription termination. Pausing and termination states are thought to arise through a common, elemental pause state that is inhibitory for nucleotide addition. We report three crystal structures of Thermus RNAP elemental paused elongation complexes (ePECs). The structures reveal the same relaxed, open-clamp RNAP conformation in the ePEC that may arise by failure to re-establish DNA contacts during translocation. A kinked bridge-helix sterically blocks the RNAP active site, explaining how this conformation inhibits RNAP catalytic activity. Our results provide a framework for understanding how RNA hairpin formation stabilizes the paused state and how the ePEC intermediate facilitates termination.</p>