Enterococcus faecalis Virulence Regulator FsrA Binding to Target Promoters

Abstract

The FsrABDC signal transduction system is a major virulence regulator in Enterococcus faecalis. The FsrC sensor histidine kinase, upon activation by the gelatinase biosynthesis-activating pheromone (GBAP) peptide encoded by the fsrBD genes, phosphorylates the FsrA response regulator required for the transcription of the fsrBDC and the gelE-sprE genes from the fsrB promoter and the gelE promoter, respectively. FsrA belongs to the LytTR family of proteins, which includes other virulence regulators, such as AgrA of Staphylococcus aureus, AlgR of Pseudomonas aeruginosa, and VirR of Clostridium perfringens. The LytTR DNA-binding domain that characterizes these proteins generally binds to two imperfect direct repeats separated by a number of bases that place the repeats on the same face of the DNA helix. In this study, we demonstrated that FsrA also binds to two imperfect direct repeats separated by 13 bp, based on the consensus sequence of FsrA, T/AT/CAA/GG GAA/G, which is consistent with the binding characteristics of LytTR domains.

ThefsrQuorum-Sensing System and Cognate Gelatinase Orchestrate the Expression and Processing of Proprotein EF_1097 into the Mature Antimicrobial Peptide Enterocin O16

“…Eleven of these showed enterocin O16-like activity and had an intact fsr regulatory pathway. Consistent with previous reports (11,27), we show by functional genetic analysis that ef1097 is regulated by the fsr system and that, in the absence of intact fsr signaling, the production of the EF_1097 precursor protein and the factors required for its maturation was compromised.…”

“…DNA sequencing of the ef1097 locus of E. faecalis O16 revealed no major differences from the ef1097 sequences of other E. faecalis strains in the promoter region or in the putative translated product (data not shown). Sequence analyses identified two imperfect direct repeats with identity to the sequences found in the fsr-regulated promoters (11). Putative Ϫ10 and Ϫ35 sequences, as well as transcription start and ribosomal binding sites, were identified (Fig.…”

“…Analysis of the ef1097 DNA sequences (including the promoter region) revealed that only Merz96 had one nucleotide substitution that could explain the absence of antimicrobial activity; this mutation produces a 5= truncation of ef1097, thereby using an alternate translation initiation. Since the ef1097 gene is subject to the fsr regulatory system (11,27), the genomes were investigated with respect to the integrity of the fsrABCD genes and gelatinase production. It was evident that all bacteriocin-positive strains except X98 inherited an intact fsr regulatory system and produced gelatinase.…”

“…Accumulated GBAP is recognized by the sensor histidine kinase FsrC, which in turn activates the response regulator FsrA by phosphorylation. FsrA acts as a transcription factor upregulating the expression of three primary target loci (fsrBCD, gelE-sprE operons, and ef1097) (11). The fsr regulatory system thus controls the expression of the GelE and SprE proteases, which are implicated in several aspects of E. faecalis physiology, including protein turnover, biofilm formation, and virulence (12)(13)(14).…”

Molecular Insights into the Control of Transcription Initiation at the Staphylococcus aureus agr operon

“…19 AgrA, the master transcription activator of the agr operon, belongs to a family (LytTR family) of relatively poorly characterised transcription regulators that are mostly involved in the activation of virulence genes (examples include Pseudomonas aeruginosa AlgR, Clostridium perfringens VirR, Streptococcus pneumoniae BlpR and Enterococcus faecalis FsrA). 8,41,42 The results of this study have demonstrated, for the first time, that transcription initiation can occur from the agr operon promoters P2 and P3 in an AgrA-independent manner. The results also provide the first molecular insights into how AgrA might control transcription initiation at the agr operon in S. aureus.…”