title: Ancient RNA stems that terminate transcription.
abstract: Multi-subunit RNA polymerases are the enzymes that perform transcription in all living organisms and that have emerged before the divergence of domains of life. The structures of catalytic cores and their functions during elongation step of transcription cycle are very similar for all multi-subunit RNA polymerases. In contrast, the mechanisms for terminating the RNA synthesis have seemingly diverged in modern RNA polymerases. However, the recent finding that, much like during bacterial transcription, RNA secondary structure is involved in termination by eukaryotic RNA polymerase III (pol III), suggests that RNA-dependent termination may have emerged before the divergence of bacterial and archaeal/eukaryotic RNA polymerases. In the case of pol III, the terminating RNA secondary structures are not dedicated hairpins, but are formed by the bodies of highly structured transcripts, which are clearly the remnants from the RNA-protein world. Here I discuss the similarities and differences of RNA-dependent mechanisms of termination of transcription by bacterial RNA polymerase and pol III.
authors.affiliation: Centre for Bacterial Cell Biology; Institute for Cell and Molecular Biosciences; Newcastle University; Baddiley-Clark Building; Newcastle upon Tyne, UK.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Zenkin
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005786:Gene Expression Regulation; D055029:Inverted Repeat Sequences; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D012320:RNA Polymerase III / Q000378:metabolism; D061806:Transcription Termination, Genetic
chemical_list: D012313:RNA; D012321:DNA-Directed RNA Polymerases; D012320:RNA Polymerase III
keywords: Last Universal Common Ancestor; RNA hairpin; RNA polymerase; RNA secondary structure; elongation complex; molecular evolution; pausing; termination; transcription