PMID:8981985

Citation	Arthur, M, Depardieu, F, Gerbaud, G, Galimand, M, Leclercq, R and Courvalin, P (1997) The VanS sensor negatively controls VanR-mediated transcriptional activation of glycopeptide resistance genes of Tn1546 and related elements in the absence of induction. J. Bacteriol. 179:97-106
Abstract	Transposon Tn1546 from Enterococcus faecium BM4147 encodes a histidine protein kinase (VanS) and a response regulator (VanR) that regulate transcription of the vanHAX operon encoding a dehydrogenase (VanH), a ligase (VanA), and a D,D-dipeptidase (VanX). These last three enzymes confer resistance to glycopeptide antibiotics by production of peptidoglycan precursors ending in the depsipeptide D-alanyl-D-lactate. Transcription of vanS and the role of VanS in the regulation of the vanHAX operon were analyzed by inserting a cat reporter gene into vanS. Transcription of cat and vanX was inducible by glycopeptides in partial diploids harboring vanS and vanS(omega)cat but was constitutive in strains containing only vanS(omega)cat. Promoters P(R) and P(H), located upstream from vanR and vanH, respectively, were cloned into a promoter probing vector to study transactivation by chromosomally encoded VanR and VanS. The promoters were inactive in the absence of vanR and vanS, inducible by glycopeptides in the presence of both genes, and constitutively activated by VanR in the absence of VanS. Thus, induction of the vanHAX operon involves an amplification loop resulting from binding of phospho-VanR to the P(R) promoter and increased transcription of the vanR and vanS genes. Full activation of P(R) and P(H) by VanR was observed in the absence of VanS, indicating that the sensor negatively controls VanR in the absence of glycopeptides, presumably by dephosphorylation. Activation of the VanR response regulator in the absence of VanS may involve autophosphorylation of VanR with acetyl phosphate or phosphorylation by a heterologous histidine protein kinase.
Links	PubMed PMC178666
Keywords	Anti-Bacterial Agents/pharmacology; Bacterial Proteins/biosynthesis; Bacterial Proteins/genetics; Chloramphenicol O-Acetyltransferase/genetics; Conjugation, Genetic; DNA Transposable Elements/genetics; Dipeptidases/biosynthesis; Drug Resistance, Microbial/genetics; Enterococcus faecalis/genetics; Enterococcus faecium/drug effects; Enterococcus faecium/enzymology; Enterococcus faecium/genetics; Gene Expression Regulation, Bacterial/drug effects; Gene Expression Regulation, Bacterial/genetics; Genes, Reporter/genetics; Glycopeptides; Molecular Sequence Data; Multigene Family/genetics; Mutation; Operon/genetics; Polymorphism, Restriction Fragment Length; Promoter Regions, Genetic/genetics; Protein Kinases/genetics; Protein Kinases/physiology; Recombinant Fusion Proteins; Serine-Type D-Ala-D-Ala Carboxypeptidase; Transcription Factors/genetics; Transcription Factors/physiology; Transcriptional Activation/drug effects; Transcriptional Activation/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ENTFC:VANA		GO:0008716: D-alanine-D-alanine ligase activity	ECO:0000314:		F		VanA is a ligase that binds D-Ala with D-Ala	complete CACAO 11320
ENTFC:VANX		GO:0010628: positive regulation of gene expression	ECO:0000314:		P		Fig. 4 shows production of VanX can be induced by different vancomycin concentrations. Expression of VanX is positively regulated in presence of vancomycin.	complete CACAO 11321
ENTFC:VANR		GO:0043433: negative regulation of sequence-specific DNA binding transcription factor activity	ECO:0000316:	UniProtKB:Q06240	P		Figure 4 shows that VanR by itself expresses the operon constitutively, and the authors conclude that VanS works by inhibiting VanR in the absence of inducer	complete CACAO 11268
ENTFC:VANS		GO:0043433: negative regulation of sequence-specific DNA binding transcription factor activity	ECO:0000316:	UniProtKB:Q06239	P		Figure 4 shows that VanR by itself expresses the operon constitutively, and the authors conclude that VanS works by inhibiting VanR in the absence of inducer	complete CACAO 11269
ENTFC:C7EME7	Contributes to	GO:0010628: positive regulation of gene expression	ECO:0000314:		P		Figure 3 shows bar graphs that contain data obtained from enzyme assays that measured the specific activity of the vanX gene at various levels of Vancomycin concentration. These graphs show that as the concentration of Vancomycin increases, the activity of vanX also increases. Since the concentration of the antibiotic effects the activity of the gene, it shows that the expression of vanX is increased as the concentration of Vancomycin increases.	complete CACAO 11293

References

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