The Yersinia enterocolitica pYV Virulence Plasmid Contains Multiple Intrinsic DNA Bends Which Melt at 37°C

Temperature has a pleiotropic effect on Yersinia enterocolitica gene expression. Temperature-dependent phenotypes include the switching between two type III protein secretion systems, flagellum biosynthesis (相似文献   

Temperature regulation of Shigella virulence: identification of the repressor gene virR, an analogue of hns, and partial complementation by tyrosyl transfer RNA (tRNA1Tyr)

virR is the central regulatory locus required for coordinate temperature-regulated virulence gene expression in the human enteric pathogens of Shigella species. Detailed characterization of VirR+ clones revealed that virR consisted of a 411 bp open reading frame (ORF) that mapped to a chromosomally located 1.8kb EcoRI-AccI DNA fragment from Shigella flexneri. Insertional inactivation of the virR ORF at a unique HpaI restriction site resulted in a loss of VirR+ activity. The virR ORF nucleotide sequence was virtually identical to the Escherichia coli hns gene, which encodes the histone-like protein, H-NS. Based on the predicted amino acid sequence of E. coli H-NS, only a single conservative base-pair change was identified in the virR gene. An additional clone, designated VirRP, which only partially complemented the virR mutation, was also characterized and determined by Southern hybridization and nucleotide sequence analysis to be unique from virR. Subclone mapping of this clone indicated that the VirRP phenotype was a result of the multiple copy expression of the S. flexneri gene for tRNA(Tyr). These data constitute the first direct genetic evidence that virR is an analogue of the E. coli hns gene, and suggest a model for temperature regulation of Shigella species virulence via the bacterial translational machinery.     

Genome organisation and chromatin structure in Escherichia coli

We have analysed the complete sequence of the Escherichia coli K12 isolate MG1655 genome for chromatin-associated protein binding sites, and compared the predicted location of predicted sites with experimental expression data from 'DNA chip' experiments. Of the dozen proteins associated with chromatin in E. coli, only three have been shown to have significant binding preferences: integration host factor (IHF) has the strongest binding site preference, and FIS sites show a weak consensus, and there is no clear consensus site for binding of the H-NS protein. Using hidden Markov models (HMMs), we predict the location of 608 IHF sites, scattered throughout the genome. A subset of the IHF sites associated with repeats tends to be clustered around the origin of replication. We estimate there could be roughly 6000 FIS sites in E. coli, and the sites tend to be localised in two regions flanking the replication termini. We also show that the regions upstream of genes regulated by H-NS are more curved and have a higher AT content than regions upstream of other genes. These regions in general would also be localised near the replication terminus.