Interaction of RNA polymerase with lacUV5 promoter DNA during mRNA initiation and elongation. Footprinting, methylation, and rifampicin-sensitivity changes accompanying transcription initiation.
J Mol Biol
; 183(2): 165-77, 1985 May 25.
Article
em En
| MEDLINE
| ID: mdl-2409292
ABSTRACT
We have used enzymatic and chemical probes to follow the movement of Escherichia coli RNA polymerase along lacUV5 promoter DNA during transcription initiation. The RNA polymerase does not escape from the promoter but remains tightly bound during the synthesis of the initial bases of the transcript. This initial phase of RNA synthesis involves the reiterative synthesis and release of RNA chains up to ten bases long via the RNA polymerase cycling reaction and the enzyme remains sensitive to rifampicin inhibition. When longer chains are made, promoter-specific binding is disrupted and the enzyme forms a rifampicin-resistant elongation complex with downstream DNA sequences. This elongation complex covers less than half as much DNA and lacks the DNase I-hypersensitive sites and the base-specific contacts that characterize promoter-bound RNA polymerase. These results lead us to suggest that lacUV5 mRNA synthesis is primed by a promoter-bound enzyme complex that synthesizes the initial nine or ten bases in the mRNA chain. Subsequently, when a chain of ten bases, or slightly longer, is made, contacts with promoter DNA are irreversibly disrupted, sigma subunit is lost, and a "true" elongation complex is formed.
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Base de dados:
MEDLINE
Assunto principal:
RNA Polimerases Dirigidas por DNA
/
RNA Bacteriano
/
RNA Mensageiro
/
Óperon Lac
Tipo de estudo:
Diagnostic_studies
Idioma:
En
Revista:
J Mol Biol
Ano de publicação:
1985
Tipo de documento:
Article