Transcriptional pattern of Escherichia coli ihfB (himD) gene expression.

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).