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  • Title: Differential melting of the transcription start site associated with changes in RNA polymerase-promoter contacts in initiating transcription complexes.
    Author: Brodolin K, Buckle M.
    Journal: J Mol Biol; 2001 Mar 16; 307(1):25-30. PubMed ID: 11243800.
    Abstract:
    Formaldehyde cross-linking was used in a kinetic analysis of RNA polymerase-lacUV5 promoter interactions in open complexes (RP(o)). RP(o) quenched from 37 degrees C to 14 degrees C isomerised to a closed, competitor resistant, complex (RP(LT)). We observed that contacts of the beta' and sigma subunits with the positions -3, -5 of the non-template DNA strand disappeared very quickly during the first 30 seconds after the temperature downshift. The re-annealing of the DNA downstream of the transcription start site takes place in the same time scale. However re-annealing of the upstream part of the transcription bubble was slower and completed within five minutes. The results support a two-step model of promoter melting and suggest that conformational changes in the RNA polymerase occur concurrently with the melting around the transcription start site.
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