RESUMO
We report the identification of integration host factor (IHF) as an additional element involved in the regulation of the cysJIH promoter of Salmonella typhimurium and Escherichia coli. An IHF-binding site was located in the regulatory region of the cysJIH promoter by using two methods, protection against DNase I digestion and hydroxyl radical cleavage. The positive influence of IHF on in vitro run-off transcription from the cysJIH promoter is shown. The in vivo observations suggest that IHF is necessary for full expression of cysJIH in stationary phase but not during exponential growth.
Assuntos
Proteínas de Bactérias/farmacologia , Cisteína/biossíntese , Escherichia coli/genética , Regulação da Expressão Gênica , Salmonella typhimurium/genética , Sequência de Bases , Sítios de Ligação , Fatores Hospedeiros de Integração , Dados de Sequência Molecular , Mutação , Regiões Promotoras GenéticasRESUMO
The nucleotide sequence of a chromosomal DNA fragment located upstream from the cysPTWAM operon of Escherichia coli was established. Sequence analysis indicates the presence of an open reading frame which has been designated ucpA (upstream cys P). The potential protein products exhibits strong sequence homology to the members of a large protein family, short-chain dehydrogenases/reductases. Involvement of Crp, FruR and IHF in the regulation of ucpA transcription in vivo was demonstrated.
Assuntos
Escherichia coli/genética , Genes Bacterianos , Oxirredutases/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Dados de Sequência MolecularRESUMO
Integration host factor (IHF) is a small heterodimer containing subunits encoded by the unlinked ihfA (himA) and ihfB (himD, hip) genes. The transcriptional pattern of ihfB expression in the logarithmic and stationary growth phases was investigated. The ihfB gene is expressed as both monocistronic and polycistronic (hybridizing also to an internal rpsA probe) transcript. The intensity of the polycistronic transcripts, initiated upstream of rpsA, decreased sharply upon growth cessation. In contrast, expression of the monocistronic ihfB transcript strongly increased when cells entered stationary growth phase. The observed growth rate-dependent regulation of the transcription of these transcripts is in agreement with the previously published data about the regulation of the rpsA and ihfB promoters (Pedersen et al., 1984; Aviv et al., 1994).
Assuntos
Proteínas de Bactérias/genética , Escherichia coli/genética , Transcrição Gênica , Cromossomos Bacterianos , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Fatores Hospedeiros de Integração , Regiões Promotoras Genéticas , Terminologia como AssuntoRESUMO
The E. coli AP1-200-9 strain for rapid identification of genes encoding restriction and modification enzymes carries a temperature sensitive lacZ gene fused to the damage-inducible dinD locus. A derivative of this strain was constructed that has a wild-type form of this locus which allows for a more efficient identification of recombinant plasmids encoding restriction and modifications enzymes.
