Modeling feedback loops in the H-NS-mediated regulationof the Escherichia coli bgl operon

Radde, Nicole and Gebert, Jutta and Faigle, Ulrich and Schrader, Rainer and Schnetz, Karin (2008) Modeling feedback loops in the H-NS-mediated regulationof the Escherichia coli bgl operon.
Published in: Journal of theoretical biology Vol. 250 (2). 298-306 .


The histone-like nucleoid-associated protein H-NS is a global transcriptional repressor that controls approximately 5% of all genes in {it Escherichia coli} and other Enterobacteria. H-NS binds to DNA with low specificity. Nonetheless, repression of some loci is exceptionally specific. Experimental data for the {it E.coli bgl} operon suggest that highly specific repression is caused by regulatory feedback mechanisms. To analyze whether such feedback mechanisms could account for the observed specificity of repression, a model was built based on expression data. The model includes three parameters of {it bgl} operon regulation. These are cooperativity of repression by binding of H-NS to two sites, an inverse correlation of the rate of repression by H-NS and the transcription rate, and a threshold for positive regulation by antiterminator BglG, which is encoded within the operon. The latter two parameters represent feedback loops in the model. The resulting system of equations was solved for the expression level of the operon and analyzed with respect to different promoter activities. The analysis demonstrated that the parameters included into the model are sufficient to simulate specific repression of {it bgl} by H-NS. Particularly, a small (3-fold) increase in the promoter activity resulted in a strong (80-fold) enhancement of {it bgl} operon expression. Moreover, analysis of the system's behavior for different conditions and parameter changes demonstrated that the model can exhibit hysteresis caused by the positive nonlinear feedback loop based on positive regulation by antiterminator BglG.

Full text not available from this repository. (Request a copy)
Editorial actions: View Item View Item (Login required)
Deposit Information:
ZAIK Number: zaik2007-550
Depositing User: Nicole Radde
Date Deposited: 22 Jun 2007 00:00
Last Modified: 12 Jan 2012 09:41