yst gene expression in Yersinia enterocolitica is positively regulated by a chromosomal region that is highly homologous to Escherichia coli host factor 1 gene (hfq)

Abstract

Yersinia enterocolitica produces heat-stable enterotoxin (Y-ST) as one of its virulence factors. The yst gene, however, frequently and spontaneously becomes inactive (silent) during storage, which is accompanied by concurrent changes in some biological properties such as colony morphology, growth rate, carbon fermentation and ornithine decarboxylase activity. Northern blot analysis revealed that the level of mRNA for yst was repressed. To investigate the regulatory region, we transformed a yst-silent strain with a chromosomal gene library of Y-ST producing an isogenic counterpart. Out of 3604 clones, one clone resumed the Y-ST production and concurrently other biological properties. An open reading frame in this clone was designated as yrp, yersinia regulator for pleiotropic phenotype. Deduced from the nucleotide sequence, Yrp was a small protein of I01 amino acids with no similarity with any regulatory factor described, but showed high homology with an Escherichia coli host factor 1 required for Q beta-replicase, and with an Azorhizobium caulinodans NrfA required for the expression of nifA. The yrp gene mutation caused decreased negative supercoiling of plasmids, as did hfq. The yrp gene could similarly complement Y-ST production in two other silent strains of Y. enterocolitica. In all three silent strains examined, we found various mutations in the yrp region.

Transcriptional Regulation inYersinia: An UpdateYersinia: An Update

“…For example, the oxyS gene transcript may inhibit rpoS translation by binding HF-1 and sequestering this molecule from rpoS leader RNA (Zhang et al, 1998). The H-NS histone-like protein has also been reported to antagonize rpoS mRNA translation (Yamashino et al, 1995).Regulation in Yersinia: an Update 155 and ElliottRecent studies conducted in Y. enterocolitica are consistent with this model: Yrp, the recently characterized HF-1 (Hfq) counterpart in Yersinia (also referred to as Ymr in certain databases) has been shown to control yst expression at the transcriptional level (Nakao et al, 1995). In line with these results, it was hypothesized that Yrp may exert its effect though the control of DNA topology (Nakao et al, 1995).…”

Functional replacement of the Escherichia coli hfq gene by the homologue of Pseudomonas aeruginosa

“…As shown in Fig. 1, Hfq Pa shows considerable amino acid similarity to previously identified Hfq homologues from other Gram-negative bacteria (73 to 96 %) (Brown & Elliott, 1996 ;Chuang et al, 1999 ;Deckert et al, 1998 ;Durand et al, 1997 ;Fleischmann et al, 1995 ;Kajitani & Ishihama, 1991 ;Kaminski et al, 1994 ;Nakao et al, 1995 ;Robertson & Roop, 1999), whereas lower amino acid similarity (41 to 45 %) was found with putative Hfq homologues from three Grampositive bacteria. The multiple alignment (Fig.…”

“…Taken together with the above-described effects on specific genes, these results suggested that Hfq acts as a global regulator involved in the regulation of RpoS-dependent and RpoS-independent genes. Moreover, Hfq homologues have been reported to stimulate synthesis of the heat-stable enterotoxin in Yersinia enterocolitica (Nakao et al, 1995) and of the NifA protein in Azorhizobium caulinodans (Kaminski et al, 1994). Also, the Hfq homologue of Brucella abortus appears to be a major determinant of virulence in mice (Robertson & Roop, 1999).…”

Proteome analysis of extracellular proteins regulated by the las and rhl quorum sensing systems in Pseudomonas aeruginosa PAO1

“…We were unable to observe CbpD in any mutants suggesting that (i) the reduction in cbpD transcription results in levels of CbpD that are too low to be detected by fluorescence staining of 2-DE separated proteins and/or (ii) the secretion system required to export CbpD also requires both QS systems. All mutants were deficient in the expression of PA4944, a protein with significant sequence similarity to host factor I (HF-I), an RNA-binding protein that regulates enterotoxin production in Yersinia enterocolitica (Nakao et al, 1995) and several virulence factors in Brucella abortus (Robertson & Loop, 1999). Previous reports have suggested that genes under the control of QS may also be regulated by other factors, including the alternative sigma factors RpoS (Van Delden & Iglewski, 1998) and PvdS (Ochsner et al, 1996).…”