期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2005
卷号：102
期号：12
页码：4488-4493
DOI：10.1073/pnas.0409850102
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
