Atomic Force Microscopy of Transcription Initiation Complexes Formed by Escherichia Coli RNA Polymerase PDF Download

Author: Sebastian Maurer
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Languages : en
Pages : 158

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Book Description
As much as protein - DNA interactions depend on the conformation of the binding protein they are also influenced by the local geometry of the DNA. Since the topology of DNA is continuously changing due to ongoing replication, transcription and associated fluctuations of topoisomerase activity, the accessibility and configuration of the recognition elements for proteins, the major grooves for example, are also subject to changes. Thus many protein-DNA interactions are affected by a change of the superhelicity of DNA, although to different extent. The work at hand focuses on the effect of DNA topology on regulation of gene transcription - a relationship studied on the example of two supercoiling sensitve E.Coli promoters: The fis (factor of inversion stimulation) promoter and the Tyrosine tRNA promoter. By utilizing Atomic Force Microscopy (AFM) this study demonstrates both: a complex of two RNAP molecules forming a dimer on binding to the divergent promoter module consisting of fisP1 and fisPdiv sites, as well as the structures of FIS and RNAP bound to the tyrT promoter either separately or together - thereby visualizing a ó70-RNAP containing transcription initiation complex for the first time. The models for the transcriptional activation of the fis and the tyrT promoters presented in this work were proposed under consideration of the nucleoprotein complex structures visualized by AFM and supported by further biochemical data. Despite the differences in sequence organisation of the fis and tyrT promoters, both models share a common feature: A transcription activation mechanism which acts through the optimization of the local superhelical density.