Deregulation of temperature‐dependent transcription of the invasion regulatory gene, virB, in Shigella by rho mutation
- 1 April 1994
- journal article
- Published by Wiley in Molecular Microbiology
- Vol. 12 (2) , 267-276
- https://doi.org/10.1111/j.1365-2958.1994.tb01015.x
Abstract
Expression of the virB gene, the transcriptional regulator for the invasion genes encoded by the large plasmid of Shigella flexneri, is temperature-regulated. virB transcription is under the control of VirF and H-NS, which act as positive and negative regulators, respectively, and is highly responsive to changes in DNA superhelicity. To further investigate the molecular mechanisms underlying the thermoregulation of virB transcription, a mutant which expressed an invasion phenotype at both 30° C and 37° C was isolated using miniTn10-Kan (mini KAN) random insertion mutagenesis. The insertion site was mapped to the rho gene, and resulted in the addition of 11 amino acids to the C-terminus of the Rho protein. Consequently, decreased transcription termination activity at a p-dependent terminator, λtL1, was observed, in the rho mutant, both the transcription of virB and expression of invasion genes were activated at 30°C and were less responsive to changes in temperature. The deregulation of virB expression by the mutation was dependent upon the virB promoler, since the effects of the mutation on virB transcription were abolished when its promoler region was replaced by the tac promoler. Temperature-responsive changes in DNA topology, as determined by linking numbers of a reporter plasmid, showed that changes in DNA superhelicity in the rho mutant were smaller than that in the wild type. Furthermore, when the mutant was grown in medium containing novobiocin, an inhibitor of DNA gyrase, virB transcription at 30° C as well as at 37°C was greatly diminished. These results indicated that Rho protein could have a profound effect on topological temperature-dependent changes in DNA structure, thus contributing to thermoregulation of VirS transcription.Keywords
This publication has 43 references indexed in Scilit:
- Isolation and characterization of a topA mutant of Shigella flexneriMolecular Microbiology, 1993
- Identification and characterization of virK, a virulence‐associated large plasmid gene essential for intercellular spreading of Shigella flexneriMolecular Microbiology, 1992
- Temperature regulation of Shigella virulence: identification of the repressor gene virR, an analogue of hns, and partial complementation by tyrosyl transfer RNA (tRNA1Tyr)Molecular Microbiology, 1992
- Temperature‐regulated expression of invasion genes in Shigella flexneri is controlled through the transcriptional activation of the virB gene on the large plasmidMolecular Microbiology, 1991
- Protein H1: a role for chromatin structure in the regulation of bacterial gene expression and virulence?Molecular Microbiology, 1990
- Mutant rho factors with increased transcription termination activities. IIJournal of Molecular Biology, 1989
- Functional organization and nucleotide sequence of virulence Region‐2 on the large virulence plasmid in Shigella flexneri 2aMolecular Microbiology, 1989
- A dual transcriptional activation system for the 230 kb plasmid genes coding for virulence‐associated antigens of Shigella flexneriMolecular Microbiology, 1989
- TRANSCRIPTION TERMINATION AND THE REGULATION OF GENE EXPRESSIONAnnual Review of Biochemistry, 1986
- Stabilization of the hexameric form of Escherichia coli protein rho under ATP hydrolysis conditionsJournal of Molecular Biology, 1982