Role of Escherichia Coli Histone‐Like Nucleoid‐Structuring Protein in Bacterial Metabolism and Stress Response

Abstract

The histone-like nucleoid-structuring protein, H-NS, is a major bacterial chromatin component which influences DNA structure and gene expression. Mutations in hns, the structural gene of H-NS protein, have been shown to result in highly pleiotropic effects in E.wherichiu coli cells. In this study, we have initiated an index of the proteins whose synthesis is, directly or indirectly regulated by H-NS. Using twodimensional gel electrophoresis, we have examined the global changes in gene expression which occured in an hns background compared with its wild-type parent. In addition, we analysed the effects of mutations in two other genes i.e. lrp and ptu, which are also involved in global regulatory pathways. Although these comparative analyses revealed several common differences, thus suggesting possible interactions between these regulatory mechanisms, i.e. H-NS, Lrp (leucine-responsive regulatory protein) and acetylphosphate, the most extensive modifications occurred in an hns mutant. Among the polypeptides whose level of synthesis was specifically altered in an hns mutant, several corresponded to H-NS targets previously identified by classical selection methods. Moreover, the present study allows us to characterize several H-NS targets, which were identified either by comparison with the E. coli two-dimensional reference maps or by microsequencing procedure. Many of these newly identified polypeptides are involved in adaptation of E. coli cells to environmental challenges, and one of them could be involved in bacterial virulence. Finally, synthesis of several proteins belonging to the heat-shock regulon, more particularly molecular chaperones, was induced in an hns mutant.

Regulation of bacterial motility in response to low pH in Escherichia coli: the role of H-NS protein

“…of 0n7. Total protein extracts and two-dimensional gel electrophoresis were carried out as previously described (Hommais et al, 2001 ;Laurent-Winter et al, 1997).…”

TheEscherichia coliProteome: Past, Present, and Future Prospects

“…The dissection of stimulons into regulons is based on comparison of the induction patterns in wild-type cells versus those of strains having mutations in known regulatory elements. In this way, regulators such as the RNA polymerase sigma factor RpoS (192), the histone-like protein H-NS (19,118,158), and the leucine-responsive regulatory protein Lrp (61) have been studied based on the comparative analysis of wild-type and mutant or double mutant strains.…”

Differential expression of the cyclin-dependent kinase inhibitor P27 in primary hepatocytes in early-mid G1 and G1/S transitions

“…Samples were then lyophilized and resuspended in 10 ml of sample buer composed of 9.95 M urea, 4% Nonidet P-40, 2% ampholytes and 100 mM DTT, and stored at 7808C until used. Twodimensional gel electrophoresis was carried out essentially as described previously (Laurent-Winter et al, 1997). Prior to electrophoresis, samples were centrifuged for 2 min, then 10 ml of sample containing 50 mg of proteins were loaded onto the isoelectric focusing (IEF) gel (pH range 3 ± 10 ampholytes, Millipore Inc.), and focused for 20 000 Vh.…”