Disease relevance of hns

• In addition to the hns gene, the chromosome of E. coli and other enteric bacteria also includes the stpA gene that encodes the StpA protein, an H-NS paralogue [1].
• The presence of a conserved CCAAT element in the hns promoter region, on the other hand, was found not to be stringently required for cold shock activation since expression of E coli of an hns-cat fusion containing the Proteus vulgaris hns promoter lacking a CCAAT box increased over four-fold after cold shock [2].
• Characterization of hns genes from Erwinia amylovora [3].
• The Pseudomonas aeruginosa pilG gene, encoding a protein which is involved in pilus production, was cloned by phenotypic complementation of a unique, pilus-defective mutant of strain PAO1 [4].
• At a high infection dose, hns mutants trigger more sudden lethality due to their increased acute toxicity in murine urinary tract infection and sepsis models [5].

High impact information on hns

• We have now identified and characterized a new regulatory locus (drdX) and show that a histone-like bacterial protein has an important role in this novel example of thermoregulation of transcription [6].
• In an hns mutant E.coli derivative stpA expression is derepressed, suggesting that regulation of the two genes is coupled [7].
• Here we show that DsrA enhances hns mRNA turnover yet stabilizes rpoS mRNA, either directly or via effects on translation [8].
• We demonstrate that DsrA acts via specific RNA:RNA base pairing interactions at the hns locus to antagonize H-NS translation [9].
• The frequency of point mutations is not modified in bglY mutant strains [10].

Chemical compound and disease context of hns

• Transcriptional expression of Escherichia coli glutamate-dependent acid resistance genes gadA and gadBC in an hns rpoS mutant [11].
• 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 [12].

Biological context of hns

• The majority of the mutations that caused a Lac+ phenotype mapped to the hns gene, encoding the nucleoid-structuring protein H-NS [13].
• The nucleotide sequence of osmZ is almost identical to that of hns; however, hns was incorrectly located at 6.1 min on the E. coli linkage map [14].
• A class of trans-acting mutations, which alter the osmoregulated expression of the Escherichia coli proU operon, maps at 27 min on the chromosome in a locus we have called osmZ [14].
• We also analyzed H-NS isoform composition expressed by various hns mutations and found that the N-terminal 67 amino acids were sufficient to support posttranslational modification and that substitutions at positions 18 and 26 resulted in the expression of a single H-NS isoform [15].
• It also emerged that hns transcription is under negative autoregulation, at least in the logarithmic growth phase [16].

Anatomical context of hns

• Inactivation of the global regulatory hns gene counteracts increased production of LPS and flagella in response to anoxia and allows E. coli W3100 to attach to sand columns even when it is grown under oxygen-limited conditions [17].
• Mutations in hns reduce the adherence of Shiga toxin-producing E. coli 091:H21 strain B2F1 to human colonic epithelial cells and increase the production of hemolysin [18].

Associations of hns with chemical compounds

• 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 [19].

Regulatory relationships of hns

• To understand the relationship between H-NS structure and function, we transformed a cloned hns gene into a mutator strain and collected a series of mutant alleles that failed to repress proU expression [15].
• In curli-deficient, RpoS- E. coli K-12 strains, csgA is transcriptionally activated by mutations in hns, which encodes the histone-like protein H-NS [20].
• The effect of the topA mutation could be suppressed by an hns mutation, so topoisomerase I might be required to counteract the effect of H-NS protein on gene expression, in addition to its influence on RpoS-dependent transcription [21].

Other interactions of hns

• Transcription of chiA in vivo is driven by a single sigma70 promoter and is derepressed in an hns mutant [13].
• Uninduced expression of the osmE-lac fusion was increased in the presence of mutations in the hns and himA genes [22].
• Furthermore, the reduced activity of relAP2-lacZ in an hns mutant could be rescued by an rpoS mutation, which is sufficient to derepress the relAP2-lacZ activity [23].
• To gain an insight into the regulation of the hns gene itself, we constructed in this study a hns-lacZ transcriptional fusion gene and inserted a single copy at the att lambda locus on the E. coli chromosome [16].
• This study reports the characterization of a plasmid isolated from an Escherichia coli library that suppresses the effect of an hns mutation on cadA expression [24].

Analytical, diagnostic and therapeutic context of hns

• Using two-dimensional gel electrophoresis, we have examined the global changes in gene expression which occured in an hns background compared with its wild-type parent [19].
• A chromosomal hns gene was amplified with PCR consensus primers and localized near galU of E. amylovora [3].
• Electrophoretic mobility shift assays indicate that H-NS binds preferentially to the tra promoter region, while Northern blot and transcriptional fusion analyses indicate that transcription of traY, the first gene in the tra operon, is derepressed in an hns mutant throughout growth [25].
• Moreover, we found by gene fusion and Northern blot hybridization that the "histone-like" protein, H-NS, bound specifically to a promoter segment of lrp in vitro, and the level of lrp expression increased in the hns null mutant [26].
• The Escherichia coli hns mutant carrying S. marcescens hemolysin genes on a plasmid constructed by ligation of the 3.2-kb HindIII-SacI fragment of pR02 into pBluescriptIIKS, showed a high level of expression of this hemolytic factor [27].

References