Gene regulation by H-NS as a function of growth conditions depends on chromosomal position in Escherichia coli.
Bottom Line: Our results show that the activity of the Phns promoter depends on whether it is placed within the AT-rich regions of the genome that are known to be bound preferentially by H-NS.This modulation of gene expression moreover depends on the growth phase and the growth rate of the cells, reflecting the changes taking place in the relative abundance of different nucleoid proteins and the inherent heterogeneous organization of the nucleoid.Genomic position can thus play a significant role in the adaptation of the cells to environmental changes, providing a fitness advantage that can explain the selection of a gene's position during evolution.
Affiliation: LBPA, UMR 8113 du CNRS, Ecole Normale Supérieure de Cachan, Cachan, France School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.Show MeSH
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Mentions: The activity of the Phns promoter depends on the activation by the FIS protein in early exponential phase at fast growth (Falconi et al. 1996), Cold shock protein A (CspA) for induction upon cold shock (La Teana et al. 1991), and on the binding of the H-NS protein itself resulting in repression (Ueguchi et al. 1993; Falconi et al. 1993). Binding of the H-NS protein along the genome is not uniform and changes as a function of the growth phase (Kahramanoglou et al. 2011; Zarei et al. 2013). When the sites of insertion of the reporter construct are mapped on the H-NS binding patterns one can see that those sites that are less expressed (LT and RO) are found in regions with a greater probability of H-NS binding as measured by formaldehyde crosslinking (Figure 6 and Figure S4).
Affiliation: LBPA, UMR 8113 du CNRS, Ecole Normale Supérieure de Cachan, Cachan, France School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.