P Bertin, P Lejeune, C Laurent-Winter, A Danchin
Mutations in bglY, the structural gene for the DNA-binding protein H1, affect expression of several Escherichia coli genes
Biochimie (1990) 72: 889-891 

P Lejeune, A Danchin
Mutations in the bglY gene increase the frequency of spontaneous deletions in Escherichia coli K-12
Proc Natl Acad Sci U S A (1990) 87: 360-363 

P Bertin, P Lejeune, C Colson, A Danchin
Mutations in bglY, the structural gene for the DNA-binding protein H1 of Escherichia coli, increase the expression of the kanamycin resistance gene carried by plasmid pGR71
Mol Gen Genet (1992) 233: 184-192 

P Bertin, E Terao, EH Lee, P Lejeune, C Colson, A Danchin, E Collatz
The H-NS protein is involved in the biogenesis of flagella in Escherichia coli
J Bacteriol (1994) 176: 5537-5540 

JR Landgraf, M Levinthal, A Danchin
The role of H-NS in one carbon metabolism
Biochimie (1994) 76: 1063-1070 

M Levinthal, P Lejeune, A Danchin
The H-NS protein modulates the activation of the ilvIH operon of Escherichia coli K12 by Lrp, the leucine regulatory protein
Mol Gen Genet (1994) 242: 736-743 

A Danchin, E Krin
Filling the gap between hns and adhE in Escherichia coli K12
Microbiology (1995) 141 ( Pt 4): 959-960 

C Laurent-Winter, P Lejeune, A Danchin
The Escherichia coli DNA-binding protein H-NS is one of the first proteins to be synthesized after a nutritional upshift
Res Microbiol (1995) 146: 5-16 

C Laurent-Winter, S Ngo, A Danchin, P Bertin
Role of Escherichia coli histone-like nucleoid-structuring protein in bacterial metabolism and stress response--identification of targets by two-dimensional electrophoresis
Eur J Biochem (1997) 244: 767-773 

P Bertin, N Benhabiles, E Krin, C Laurent-Winter, C Tendeng, E Turlin, A Thomas, A Danchin, R Brasseur
The structural and functional organization of H-NS-like proteins is evolutionarily conserved in gram-negative bacteria
Mol Microbiol (1999) 31: 319-329 

O Soutourina, A Kolb, E Krin, C Laurent-Winter, S Rimsky, A Danchin, P Bertin
Multiple control of flagellum biosynthesis in Escherichia coli: role of H-NS protein and the cyclic AMP-catabolite activator protein complex in transcription of the flhDC master operon
J Bacteriol (1999) 181: 7500-7508 

C Tendeng, C Badaut, E Krin, P Gounon, S Ngo, A Danchin, S Rimsky, P Bertin
Isolation and characterization of vicH, encoding a new pleiotropic regulator in Vibrio cholerae
J Bacteriol (2000) 182: 2026-2032 

P Bertin, F Hommais, E Krin, O Soutourina, C Tendeng, S Derzelle, A Danchin
H-NS and H-NS-like proteins in Gram-negative bacteria and their multiple role in the regulation of bacterial metabolism
Biochimie (2001) 83: 235-241

F Hommais, E Krin, C Laurent-Winter, O Soutourina, A Malpertuy, JP Le Caer, A Danchin, P Bertin
Large-scale monitoring of pleiotropic regulation of gene expression by the prokaryotic nucleoid-associated protein, H-NS
Mol Microbiol (2001) 40: 20-36  

F Hommais, C Laurent-Winter, V Labas, E Krin, C Tendeng, O Soutourina, A Danchin, P Bertin
Effect of mild acid pH on the functioning of bacterial membranes in Vibrio cholerae
Proteomics (2002) 2: 571-579 

OA Soutourina, E Krin, C Laurent-Winter, F Hommais, A Danchin, PN Bertin
Regulation of bacterial motility in response to low pH in Escherichia coli: the role of H-NS protein
Microbiology (2002) 148: 1543-1551  

C Tendeng, OA Soutourina, A Danchin, PN Bertin
MvaT proteins in Pseudomonas spp.: a novel class of H-NS-like proteins
Microbiology (2003) 149: 3047-3050  

C Tendeng, E Krin, OA Soutourina, A Marin, A Danchin, PN Bertin
A Novel H-NS-like protein from an antarctic psychrophilic bacterium reveals a crucial role for the N-terminal domain in thermal stability
J Biol Chem (2003) 278: 18754-18760 

F Hommais, E Krin, JY Coppée, C Lacroix, E Yeramian, A Danchin, P Bertin
GadE (YhiE): a novel activator involved in the response to acid environment in Escherichia coli
Microbiology (2004) 150: 61-72  

C Médigue, E Krin, G Pascal, V Barbe, A Bernsel, PN Bertin, F Cheung, S Cruveiller, S D'Amico, A Duilio, G Fang, G Feller, C Ho, S Mangenot, G Marino, J Nilsson, E Parrilli, EPC Rocha, Z Rouy, A Sekowska, ML Tutino, D Vallenet, G von Heijne, A Danchin
Coping with cold: the genome of the versatile marine Antarctica bacterium Pseudoalteromonas haloplanktis TAC125
Genome Res (2005) 15: 1325-1335

E Krin, S Derzelle, K Bedard, M Adib-Conquy, E Turlin, P Lenormand, M-F Hullo, I Bonne, N Chakroun, C Lacroix, A Danchin
Regulatory role of UvrY in adaptation of Photorhabdus luminescens growth inside the insect
Environmental Microbiology (2008) 10: 1118–1134 

Y Jin, RM Watt, A Danchin, JD Huang
Small noncoding RNA GcvB is a novel regulator of acid resistance in Escherichia coli
BMC Genomics (2009) 10: 165 

Control of flagellum biosynthesis
The swarming properties of E. coli hns strains are altered on semi-solid medium (Figure 1 because of a lack of flagella (Figure 2. Their synthesis requires the expression numerous genes organized in an ordered cascade. Their expression is strongly reduced in a hns mutant. This suggests that H-NS is required, directly or indirectly, in the expression of flagellum biosynthesis genes (4). Furthermore this is the first example showing that this regulatory protein may have directly or indirectly a positive control on gene expression.
Figure 1 : The presence of flagella visualized by scanning electron microscopy of wild-type (A) and hns (B) strains. (4)		Figure 2 : Motility test performed on E. coli wild-type and hns strains on semi-solid-medium. (4)
The H-NS protein affects the expression of flhDC master operon which governs all flagellar genes. This mechanism is disctinct from the activation by the CAP/cAMP complex (8), ), requires the presence of an extended untranslated 5’ region (Figure 3 and is independent of StpA protein. (10).
Figure 3: Regulatory region of flhDC master operon (8). The nucleotides are numbered relative to the transcriptional start site (+1). The CAP consensus sequence is indicated in red. Regions protected by H-NS are underlined by blue lines. The positions of the -10 and -35 boxes are indicated in yellow. The ATG translational initiation codon and the putative ribosome binding site (RBS) are indicated in green.
In V. cholerae, overexpression of the orthologous VicH protein strongly reduces motility. This, again, suggests a role for this H-NS-like protein in the control of motility. (9)

H-NS-mediated global regulation of gene expression
In prokaryotes, the role of nucleoid-associated proteins in bacterial physiology remains largely unknown. H-NS has been initially isolated as a RNA polymerase associated factor. It is a polyanion binding protein that may have several regulatory targets Protein profiles (Proteome analysis) and RNA expression profiles (Transcriptome analysis) of wild-type and hns strains were compared in Escherichia coli (11) The expression of approximately 5% of the genes (Table 1) and/or the accumulation of the corresponding proteins are directly or indirectly altered in the mutant strain. About 1/5 of these genes encode proteins involved in transcription and translation, in particular many regulators. This suggests that H-NS is located at a high level in the hierarchy of regulation.(Figure 4) One third of these genes are known or were predicted in silico to encode cell envelope components or proteins usually involved in bacterial adaptation to changes in environmental conditions, such as low pH or high osmolarity. This suggets a strong relationship between the H-NS regulon and the maintenance of intracellular homeostasis
Figure 4: Functional classification of H-NS-regulated genes.
Protein profile of a hns defective mutant in Escherichia coli
By two-dimensional electrophoresis, the synthesis and/or the accumulation of numerous proteins was shown to be specifically affected by the hns mutation (2). Many proteins were identified by microsequencing procedure (5) or, more recently, by mass spectrometry (11). Most of them are involved in the adaptation of microorganisms to environmental stresses such as temperature, pH or osmolarity.
A
B
Figure 5 : 2D gel electrophoresis of proteins extracted from wild-type (A) and hns (B) E. coli strains . (11) In comparison with its wild-type counterpart, the accumulation level of proteins in green is reduced in hns strain while proteins in red are preferentially accumulated.
Structure-function-evolution of H-NS-like proteins
The three-dimensional structure of H-NS protein has not been yet determined, excepted for the C-terminal domain. Nevertheless, in silico analysis suggests that this protein contains 2 domains: the N-terminal part is predicted to be mainly a-helical and to adopt a coiled-coil structure which could play a role in oligomerisation and the C-terminal DNA-binding domain which is predicted as a mixed a-b structure. (Figure 6)
	A
	B
Figure 6: Prediction of secondary structure by the MLRC method (A) and of coiled-coil structure by the COILS program (B).
In silico analysis performed on H-NS-like proteins of various microorganisms (6,7,9,10) but also in vivo experiments (complementation of phenotypic alterations associated with a hns mutation in E. coli) suggest that they are structurally related (7). The C-terminal part which is the most conserved region has been demonstrated to interact with DNA (Figure 7). All proteins show a preferential binding to curved DNA and, despite a low conservation in their N-terminal part, an ability to dimerize in vitro. These results demonstrate that a family of proteins structurally and functionally related to H-NS of E. coli exists in microorganisms, at least in Gram-negative bacteria (6,7,9,10).
Figure 7: Amino acid sequence alignment of the C-terminal domain of H-NS and related proteins. Strictly conserved residues are indicated in red. (10)