Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 12, Pages 4488-4493Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0409850102
Keywords
transcription; promoter escape; sigma region 4; bacteriophage lambda; P-R '
Categories
Funding
- NIGMS NIH HHS [GM44025, R01 GM041376, GM41376, R01 GM064530, R01 GM044025, GM64530, R37 GM041376] Funding Source: Medline
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The sigma-subunit of bacterial RNA polymerase (RNAP) is required for promoter-specific transcription initiation. This function depends on specific intersubunit interactions that occur when sigma associates with the RNAP core enzyme to form RNAP holoenzyme. Among these interactions, that between conserved region 4 of sigma and the flap domain of the RNAP beta-subunit (beta-flap) is critical for recognition of the major class of bacterial promoters. Here, we describe the isolation of amino acid substitutions in region 4 of Escherichia coli sigma(70) that have specific effects on the sigma(70) region 4/beta-flap interaction, either weakening or strengthening it. Using these sigma(70) mutants, we demonstrate that the sigma region 4/beta-flap interaction also can affect events occurring downstream of transcription initiation during early elongation. Specifically, our results provide support for a structure-based proposal that, when bound to the beta-flap, sigma region 4 presents a barrier to the extension of the nascent RNA as it emerges from the RNA exit channel. Our findings support the view that the transition from initiation to elongation involves a staged disruption of sigma-core interactions.
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