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Gene Review

ihfA  -  integration host factor (IHF), DNA-binding...

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK1710, JW1702, hid, himA
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Disease relevance of ihfA

  • Sequence of the Escherichia coli pheST operon and identification of the himA gene [1].
  • For a representative group of these mutations, complementation by a plasmid carrying the himA+ gene or by a lambda hip+ transducing phage confirmed their identification as himA or hip mutations, respectively [2].
  • Here, we show that growth of T4 phage is inhibited both in hupA hupB and himA himD double mutants [3].

High impact information on ihfA

  • Using a narG-lacZ reporter fusion to evaluate narGHJI expression in vivo both the nitrate and anaerobic dependent controls were severely impaired in a himA mutant compared with the wild type strain [4].
  • However, the presence of a secondary promoter able to express himA and located within pheT is demonstrated [5].
  • Dual level control of the Escherichia coli pheST-himA operon expression. tRNA(Phe)-dependent attenuation and transcriptional operator-repressor control by himA and the SOS network [5].
  • Previously observed SOS induction of the himA expression is shown to occur through the modulation of both promoter activities [5].
  • Identification of a potential integration host factor binding site and repression studies of a himA mutant support the notion that integration host factor binding normally exerts a negative effect on tyrosine-mediated repression [6].

Biological context of ihfA

  • The nucleotide sequence of the 3,410-base-pair HindIII-HincII DNA fragment carrying a portion of the himA gene and the entire btuCED region was determined [7].
  • Another open reading frame (prp) was revealed downstream from pheT which was identified as himA, the gene for the alpha subunit of the integration host factor [1].
  • Our results confirm the autoregulation of himA previously described, and demonstrate that it occurs through the modulation of the secondary promoter activity within pheT [5].
  • Plasmids expressing HU-2 had a surprising phenotype; they caused growth arrest when they were introduced into E. coli strains bearing a himA or hip mutation [8].
  • Bacteriophage phi 80 and lambda-phi 80 hybrid phage of the type lambda (QSR)80, in which the rightmost 10% of the lambda genome is replaced by corresponding phi 80 material, are unable to grow lytically in himA and hip/himD mutants of Escherichia coli K12 at 32 degrees [9].

Associations of ihfA with chemical compounds

  • All the 86 mutations induced by insertion of Tn5 or a kanamycin-resistant derivative of Tn10 and approximately one-third of the spontaneous mutations were found by P1 transduction to be linked to either zdh-201::Tn10 or Tn10-1230, indicating their location in or near himA or hip, respectively [2].
  • The same deletion in himA did not cause derepression of sodA-lacZ during anaerobic growth, but resulted in an increased response (about twofold) to the presence of 2,2'-dipyridyl compared to the isogenic wild-type strain [10].

Other interactions of ihfA

  • Maintenance and stability of various plasmids, mini-P1 plasmids, mini-F plasmids, and oriC plasmids, were studied in the hupA and hupB mutants (HU mutants), and himA and hip mutants (IHF mutants) [11].
  • Experiments with himA and fis mutant strains indicated that the IHF and FIS proteins are not required for the normal osmoregulation of proU expression [12].
  • The observation that an alteration in Nul suppresses the inhibition of growth in the double himA/gyrB mutant implicates DNA gyrase, as well as integration host factor, in the DNA:protein interactions that occur at the initiation of packaging [13].


  1. Sequence of the Escherichia coli pheST operon and identification of the himA gene. Mechulam, Y., Fayat, G., Blanquet, S. J. Bacteriol. (1985) [Pubmed]
  2. Mutants of Escherichia coli defective for replicative transposition of bacteriophage Mu. Ross, W., Shore, S.H., Howe, M.M. J. Bacteriol. (1986) [Pubmed]
  3. Mutations in HU and IHF affect bacteriophage T4 growth: HimD subunits of IHF appear to function as homodimers. Zablewska, B., Kur, J. Gene (1995) [Pubmed]
  4. Activation of the Escherichia coli nitrate reductase (narGHJI) operon by NarL and Fnr requires integration host factor. Schröder, I., Darie, S., Gunsalus, R.P. J. Biol. Chem. (1993) [Pubmed]
  5. Dual level control of the Escherichia coli pheST-himA operon expression. tRNA(Phe)-dependent attenuation and transcriptional operator-repressor control by himA and the SOS network. Mechulam, Y., Blanquet, S., Fayat, G. J. Mol. Biol. (1987) [Pubmed]
  6. Regulation of aroL expression by TyrR protein and Trp repressor in Escherichia coli K-12. Lawley, B., Pittard, A.J. J. Bacteriol. (1994) [Pubmed]
  7. Nucleotide sequence of the btuCED genes involved in vitamin B12 transport in Escherichia coli and homology with components of periplasmic-binding-protein-dependent transport systems. Friedrich, M.J., de Veaux, L.C., Kadner, R.J. J. Bacteriol. (1986) [Pubmed]
  8. Primary structure and mapping of the hupA gene of Salmonella typhimurium. Higgins, N.P., Hillyard, D. J. Bacteriol. (1988) [Pubmed]
  9. A phi 80 function inhibitory for growth of lambdoid phage in him mutants of Escherichia coli deficient in integration host factor. I. Genetic analysis of the Rha phenotype. Mozola, M.A., Friedman, D.I. Virology (1985) [Pubmed]
  10. Binding of integration host factor (IHF) to the Escherichia coli sodA gene and its role in the regulation of a sodA-lacZ fusion gene. Presutti, D.G., Hassan, H.M. Mol. Gen. Genet. (1995) [Pubmed]
  11. Maintenance of plasmids in HU and IHF mutants of Escherichia coli. Ogura, T., Niki, H., Kano, Y., Imamoto, F., Hiraga, S. Mol. Gen. Genet. (1990) [Pubmed]
  12. Characterization of mutations affecting the osmoregulated proU promoter of Escherichia coli and identification of 5' sequences required for high-level expression. Lucht, J.M., Bremer, E. J. Bacteriol. (1991) [Pubmed]
  13. A point mutation in the Nul gene of bacteriophage lambda facilitates phage growth in Escherichia coli with himA and gyrB mutations. Granston, A.E., Alessi, D.M., Eades, L.J., Friedman, D.I. Mol. Gen. Genet. (1988) [Pubmed]
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