<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway"^^ . "Genetically identical cells and organisms exhibit remarkable diversity even when they have identical histories of environmental exposure. We have observed a great cell-to-cell variation in levels of proteins in an isogenic population of E. coli cells. Such gene expression noise arises from stochasticity of transcription and translation and from unequal partitioning of proteins by cell division. Variations in protein levels may lead to errors in a signal transduction system that can have a detrimental effect on the output of the system. Therefore it is important to study the characteristics and the effects of gene expression noise. The chemotaxis signal transduction pathway is well suited for noise studies due to its low complexity and the fact that it is well characterized. One objective of this work was to identify the origin and time scale of gene expression noise in the chemotaxis pathway. To do so, we quantified native single cell expression levels of genes in all three classes in the hierarchy of flagella and chemotaxis genes. We observed strong correlation in expression levels of flagella and chemotaxis proteins, which suggests that gene expression noise is dominated by factors common to all chemotaxis genes. Interestingly, correlation between independent genes was also observed, revealing that global factors make the largest contribution to the observed fluctuations. It takes approximately one generation until the correlation in protein levels between mother and daughter cells is lost. Although, total protein levels vary greatly throughout the cell cycle, protein concentrations remain more stable. Thus, noise persists on a generation time scale and consequently the pathway is expected to exhibit robustness mechanisms compensating for such fluctuations. Indeed, the signalling network, although sensitive to individual protein levels, was observed to be robust against co-variation of chemotaxis proteins while apparently minimizing network complexity and cost of protein expression. Surprisingly, we observed that robustness of the pathway against the uncorrelated variations in protein levels can be enhanced by a selective pairwise coupling of individual chemotaxis genes on one mRNA, with the order of genes in E. coli, which is subject to evolutionary selection, ranking among the best in terms of noise compensation. Finally, additional topological features contributing to pathway robustness were discovered. Our experiments suggest that the activation of CheB by phosphorylation and competition between CheY and CheB for the CheA P2 binding domain, which are not essential for chemotaxis itself, have evolved primarily for compensation of non-genetic individuality."^^ . "2008" . . . . . . . . "Linda Elisabeth"^^ . "Løvdok"^^ . "Linda Elisabeth Løvdok"^^ . . . . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (PDF)"^^ . . . "2009_03_01_LLo_diss_publish.pdf"^^ . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Gene expression noise and robustness in the Escherichia coli chemotaxis pathway (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #9109 \n\nGene expression noise and robustness in the Escherichia coli chemotaxis pathway\n\n" . "text/html" . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .