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| The EMBO Journal
(1998) 17, 2877–2885, doi:10.1093/emboj/17.10.2877 |
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| Regulation of crp transcription by oscillation between distinct nucleoprotein complexes |
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| Gardenia González-Gil1, 2, 3, Regine Kahmann1, 2 and Georgi Muskhelishvili2 |
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1 Institut für Genbiologische Forschung Berlin GmbH, Ihnestrasse 63, D-14195 Berlin, Germany 2 Institut für Genetik der Universität München, Maria Wardstrasse 1a, D-80638 München, Germany 3 Present address: 635 Old Quarry Road North, Larkspur, CA 94939, USA To whom correspondence should be addressed Gardenia González-Gil, gonzalezgil@neteze.com Received 6 October 1997; Revised 11 March 1998; Accepted 11 March 1998. |
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| Abstract |
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| FIS belongs to the group of small abundant DNA-binding proteins of Escherichia coli. We recently demonstrated that, in vivo, FIS regulates the expression of several genes needed for catabolism of sugars and nucleic acids, a majority of which are also transcriptionally regulated by cAMP–cAMP-receptor protein (CRP) complex. Here we provide evidence that FIS represses transcription of the crp gene both in vivo and in vitro. Employing crp promoter–lacZ fusions, we demonstrate that both FIS and cAMP–CRP are required to keep the crp promoter in a repressed state. We have identified in the crp promoter other transcription initiation sites which are located 73, 79 and 80 bp downstream from the previously mapped start site. Two CRP- and several FIS-binding sites with different affinities are located in the crp promoter region, one of them overlapping the downstream transcription initiation sites. We show that initiation of transcription at the crp promoter is affected by the composition of nucleoprotein complexes resulting from the outcome of competition between proteins for overlapping binding sites. Our results suggest that the control of crp transcription is achieved by oscillation in the composition of these regulatory nucleoprotein complexes in response to the physiological state of the cell. |
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| Keywords: cAMP–CRP, crp promoter, FIS, nucleoprotein complex, transcriptional regulation |
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