PMID:10843842
| Citation |
Pemberton, IK, Muskhelishvili, G, Travers, AA and Buckle, M (2000) The G+C-rich discriminator region of the tyrT promoter antagonises the formation of stable preinitiation complexes. J. Mol. Biol. 299:859-64 |
|---|---|
| Abstract |
RNA polymerase forms a highly stable preinitiation complex at many prokaryotic promoters in the absence of ribonucleotides. These are often characterised by the longevity of the DNA strand-separated (open) complex in the presence of heparin. In contrast, such complexes are notoriously unstable at the promoters for rRNA and tRNA under similar conditions. The high G+C content within the DNA-melting region of these promoters has been implicated in this seemingly anomalous behaviour. Here, we used rapid-pulse UV laser photo-footprinting to monitor the transient structural intermediates formed at the Escherichia coli tyrT promoter. Promoter derivatives with A+T for G/C base substitutions within the G+C-rich discriminator region (-7 to -1) augmented the stability of complexes on both linear fragments and supercoiled plasmid DNA. Analysis of the lifetime of the preinitiation complexes as a function of the discriminator sequence reveals a direct relationship between the A+T content of the DNA-melting region and the stability of the ensuing complex. Our results are consistent with the premise that a G/C block to DNA-untwisting and/or DNA-melting operates to prevent the formation of the stable isomers that are implicated in most other transcription initiation pathways. |
| Links |
PubMed Online version:10.1006/jmbi.2000.3780 |
| Keywords |
Base Composition/genetics; Base Pairing/genetics; DNA Footprinting; DNA, Bacterial/chemistry; DNA, Bacterial/genetics; DNA, Bacterial/metabolism; DNA, Superhelical/chemistry; DNA, Superhelical/genetics; DNA, Superhelical/metabolism; DNA-Directed RNA Polymerases/metabolism; Escherichia coli/enzymology; Escherichia coli/genetics; Genes, Bacterial; Half-Life; Kinetics; Lasers; Mutation/genetics; Nucleic Acid Denaturation/genetics; Promoter Regions, Genetic/genetics; Protein Binding; RNA, Transfer, Tyr/genetics; Thermodynamics; Transcription, Genetic/genetics |
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