title: ppGpp and DksA likely regulate the activity of the extracytoplasmic stress factor sigmaE in Escherichia coli by both direct and indirect mechanisms.
abstract: One of the major signalling pathways responsible for intercompartmental communication between the cell envelope and cytoplasm in Escherichia coli is mediated by the alternative sigma factor, sigmaE. sigmaE has been studied primarily for its role in response to the misfolding of outer membrane porins. This response is essentially reactionary; cells are stressed, porin folding is disrupted, and the response is activated. sigmaE can also be activated following starvation for a variety of nutrients by the alarmone ppGpp. This response is proactive, as sigmaE is activated in the absence of any obvious damage to the cell envelope sensed by the stress signalling pathway. Here we examine the mechanism of regulation of sigmaE by ppGpp. ppGpp has been proposed to activate at least two alternative sigma factors, sigmaN and sigmaS, indirectly by altering the competition for core RNA polymerase between the alternative sigma factors and the housekeeping sigma factor, sigma70. In vivo experiments with sigmaE are consistent with this model. However, ppGpp and its cofactor DksA can also activate transcription by EsigmaEin vitro, suggesting that the effects of ppGpp on sigmaE activity are both direct and indirect.
authors: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors: Alessandra
authors: A
authors: Costanzo
authors: Herve
authors: H
authors: Nicoloff
authors: Sarah E
authors: SE
authors: Barchinger
authors: Amy B
authors: AB
authors: Banta
authors: Richard L
authors: RL
authors: Gourse
authors: Sarah E
authors: SE
authors: Ades
mesh_terms: D019677:Artificial Gene Fusion; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006159:Guanosine Tetraphosphate / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C090751:dksA protein, E coli; C063202:sporulation-specific sigma factors; D006159:Guanosine Tetraphosphate; D001616:beta-Galactosidase