Transcription elongation complex stability: the topological lock.
Transcription machinery from a variety of organisms shows striking mechanistic similarity. Both multi- and single subunit RNA polymerases have evolved an 8-10-base pair RNA-DNA hybrid as a part of a stably transcribing elongation complex. Through characterization of halted complexes that can readily carry out homopolymeric slippage synthesis, this study reveals that T7 RNA polymerase elongation complexes containing only a 4-base pair hybrid can nevertheless be more stable than those with the normal 8-base pair hybrid. We propose that a key feature of this stability is the topological threading of RNA through the complex and/or around the DNA template strand. The data are consistent with forward translocation as a mechanism to allow unthreading of the topological lock, as can occur during programmed termination of transcription.
Liu
Xiaoqing
X
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003.
Martin
Craig T
CT
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003. Electronic address: CMartin@chem.umass.edu.
D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry* / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000737:chemistry*; D014158:Transcription, Genetic / Q000502:physiology*; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
D009692:Nucleic Acid Heteroduplexes; D014764:Viral Proteins; D012313:RNA; D004247:DNA; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases