Temperature effects on RNA polymerase initiation kinetics reveal which open complex initiates and that bubble collapse is stepwise
| Autor: | Kate L. Henderson, Claire Evensen, Lindsey C. Felth, Irina A. Shkel, Cristen Molzahn, Dylan Plaskon, M. Thomas Record, Sarah Dyke |
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| Rok vydání: | 2021 |
| Předmět: |
DNA
Bacterial Models Molecular Transcription Genetic Kinetics 03 medical and health sciences chemistry.chemical_compound 0302 clinical medicine Reaction rate constant Transcription (biology) RNA polymerase Escherichia coli Nucleotide Promoter Regions Genetic Transcription factor Transcription Initiation Genetic 030304 developmental biology chemistry.chemical_classification 0303 health sciences Multidisciplinary Chemistry Escherichia coli Proteins Temperature Promoter DNA-Directed RNA Polymerases Biological Sciences Duplex (building) Biophysics Nucleic Acid Conformation 030217 neurology & neurosurgery |
| Zdroj: | Proc Natl Acad Sci U S A |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.2021941118 |
| Popis: | Transcription initiation is highly regulated by promoter sequence, transcription factors, and ligands. All known transcription inhibitors, an important class of antibiotics, act in initiation. To understand regulation and inhibition, the biophysical mechanisms of formation and stabilization of the “open” promoter complex (OC), of synthesis of a short RNA–DNA hybrid upon nucleotide addition, and of escape of RNA polymerase (RNAP) from the promoter must be understood. We previously found that RNAP forms three different OC with λP(R) promoter DNA. The 37 °C RNAP-λP(R) OC (RP(O)) is very stable. At lower temperatures, RP(O) is less stable and in equilibrium with an intermediate OC (I(3)). Here, we report step-by-step rapid quench-flow kinetic data for initiation and growth of the RNA–DNA hybrid at 25 and 37 °C that yield rate constants for each step of productive nucleotide addition. Analyzed together, with previously published data at 19 °C, our results reveal that I(3) and not RP(O) is the productive initiation complex at all temperatures. From the strong variations of rate constants and activation energies and entropies for individual steps of hybrid extension, we deduce that contacts of RNAP with the bubble strands are disrupted stepwise as the hybrid grows and translocates. Stepwise disruption of RNAP-strand contacts is accompanied by stepwise bubble collapse, base stacking, and duplex formation, as the hybrid extends to a 9-mer prior to disruption of upstream DNA–RNAP contacts and escape of RNAP from the promoter. |
| Databáze: | OpenAIRE |
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