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Modulation of CRP‐dependent transcription at the Escherichia coli acs P2 promoter by nucleoprotein complexes: anti‐activation by the nucleoid proteins FIS and IHF
Author(s) -
Browning Douglas F.,
Beatty Christine M.,
Sanstad Erik A.,
Gunn Kathryn E.,
Busby Stephen J. W.,
Wolfe Alan J.
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03824.x
Subject(s) - biology , transcription (linguistics) , nucleoid , microbiology and biotechnology , dna footprinting , transcription factor , promoter , nucleoprotein , binding site , dna binding protein , electrophoretic mobility shift assay , dna , gene , escherichia coli , genetics , gene expression , philosophy , linguistics
Summary acs encodes acetyl‐coenzyme A synthetase, a high‐affinity enzyme that allows cells to scavenge for acetate during carbon starvation. CRP activates acs transcription by binding tandem DNA sites located upstream of the major promoter, acs P2. Here, we used electrophoretic mobility shift assays and DNase I footprint analyses to demonstrate that the nucleoid proteins FIS and IHF each bind multiple sites within the acs regulatory region, that FIS competes successfully with CRP for binding to their overlapping and neighbouring sites and that IHF binds independently of either FIS or CRP. Using in vitro transcription assays, we demonstrated that FIS and IHF independently reduce CRP‐dependent acs transcription. Using in vivo reporter assays, we showed that disruption of DNA sites for FIS or deletion of DNA sites for IHF increases acs transcription. We propose that FIS and IHF each function directly as anti‐activators of CRP, each working independently at different times during growth to set the levels of CRP‐dependent acs transcription.