Transcriptional control of the agr‐dependent virulence gene regulator, RNAIII, in Staphylococcus aureus

Abstract

Many of the genes coding for extracellular toxins, enzymes and cell-surface proteins in Staphylococcus aureus are regulated by a 510 nt RNA molecule, RNAIII. Expression of the RNAIII gene is positively controlled by the closely linked agr operon, which encodes a multicomponent signal-transduction system, and by an unlinked operon called sar. We have analysed the 120 bp region that separates the RNAIII promoter, P3, from the divergent agr promoter, P2. By transcription analysis, it was shown that P3 can function in trans of the agr operon. A stretch of 53 bp upstream of P3, containing an interrupted repeat of 7 bp, was found to be required for the agr-dependent expression of RNAIII. A single cytoplasmic protein was shown to bind to at least two sites within this regulatory region. The protein, which was absent in extracts from a sarA mutant, was identified as the sarA product by N-terminal amino acid sequencing. A DNA fragment from the P2 region, encompassing an almost identical repeated DNA motif, competed for the same protein. No interaction between the regulatory DNA sequence and any agr-dependent products could be demonstrated. The results of this study suggest that P3 and P2 are controlled by a mechanism involving the binding of the SarA protein to multiple sites within the regulatory regions immediately upstream of each promoter, and the as yet unknown activity of AgrA.

Pheromone‐induced production of antimicrobial peptides in Lactobacillus

“…Some response regulators have been shown to bind to promoter regions in front of regulated genes (e.g. Peschel et al, 1993), whereas others seem to have a less direct effect (Morfeldt et al, 1996a;1996b). Whether or not the product of sppR binds to the promoters depicted in Fig.…”

Analysis of Genetic Elements ControllingStaphylococcus aureus lrgABExpression: Potential Role of DNA Topology in SarA Regulation

“…More recently, Morfeldt et al (20) hypothesized that SarA binding to the agr promoter region affects the localized superhelicity of this promoter. Interestingly, SarA exhibits moderate sequence similarity to Shigella flexneri VirF (21), which has been shown to activate virB transcription by binding upstream in a DNA topology-dependent manner (34).…”

Transmembrane Topology of AgrB, the Protein Involved in the Post-translational Modification of AgrD in Staphylococcus aureus

“…AgrC, a transmembrane protein, is a sensor kinase of the classic bacterial two component signal transduction system: the N-terminal half is the input domain that interacts with a signal molecule produced by the bacteria, and the C-terminal half is a transmitter that is autophosphorylated at a conserved histidine upon stimulation by the signal molecule (2,13,14). AgrA resembles a response regulator, which is required for the activation of both agr promoters P2 and P3 (2,7,15), although it is not clear whether AgrA binds to these two promoters directly (16,17). It is possible that either phosphorylated AgrA would bind to the agr promoters or AgrA would interact with another global regulator, SarA, to control the agr expression (17)(18)(19).…”