MsmR, a specific positive regulator of the Streptococcus pyogenes FCT pathogenicity region and cytolysin‐mediated translocation system genes

Abstract

SummaryAs a prerequisite for colonization or causing local infections, Streptococcus pyogenes (group A streptococci, GAS) need to specifically adhere to eukaryotic cell surfaces. Predominantly responsible adhesin genes are contained in a genotype-specific pattern within the FCT region of the GAS genome. In this study, MsmR, belonging to AraC/XylS type transcriptional regulators, was identified in the FCT region as a positive regulator of the major fibronectin-binding adhesin protein F2 in a serotype M49 strain. Compared with the wild-type strain, the msmR mutant showed reduced binding to immobilized fibronectin and decreased adherence to and internalization into human pharyngeal epithelial cells. These results suggested that altered levels of fibronectin-binding proteins in the mutant affect eukaryotic cell attachment and internalization. Complete transcriptome and reporter fusion assay data revealed that MsmR positively regulates FCT region genes including Nra and cytolysin-mediated translocation system genes. Consistent with the genetic data, the mutant showed attenuated streptolysin O activity and eukaryotic cell cytotoxity. Direct binding of recombinant MsmR to nga , nra/cpa and prtF 2 promoter regions was confirmed by EMSA assays. As prior analysis demonstrated the Nra regulator negatively affects gene expression from the FCT region, MsmR and Nra appear to adversely control crucial virulence factor expression in GAS and thus contribute to a fine-tuned balance between local destructive process and metastatic spreading of the bacteria.

Regulation and Function of Pilus Island 1 in Group B Streptococcus

“…The Sag0644 sequence includes an AraC-like helix-turn-helix motif in the C-terminal region that suggests it may function as a transcriptional regulator. Sag0644 has 72% identity in predicted amino acid sequence to MsmR, a positive regulator of the AraC/XylS family located in an analogous location in the Streptococcus pyogenes FCT or pilus region (22). Thus, it seems likely that sag0644 encodes an AraC-type regulator based on the genetic arrangement, sequence similarity, and presence of a characteristic DNA-binding motif.…”

Peroxide Stimulon and Role of PerR in Group A Streptococcus

“…MsmR activates the pilus operon and nra (50), whereas Nra represses the pilus operon and its own expression (34,53). Regulation of the two genes was analyzed by qRT-PCR using RNA samples obtained from peroxide-treated and untreated wild-type strain 003Sm and primers designed on the basis of M-type 3 genome sequences.…”

“…Pili have been associated with adherence to human tonsil epithelium and to primary human epithelial cells in vitro (1, 44); thus, increased expression elicited by ROS during throat colonization would augment GAS adherence to the pharyngeal mucosa and promote establishment of infection. Upregulation of MsmR could have extra implications on colonization, as it is known to activate expression of fibronectinbinding proteins and other adhesins, in addition to the pilus (50). Increased FCT locus expression in M-type 3, but not M-type 1, GAS predicts strain-dependent effects of peroxide on pilus and other MsmR-regulated loci.…”

The Streptococcal Blr and Slr Proteins Define a Family of Surface Proteins with Leucine-Rich Repeats: Camouflaging by Other Surface Structures

“…Analysis of this problem was focused on two S. pyogenes surface proteins, the antiphagocytic M protein and the fibronectin-binding protein F (also known as Sfb1) (9,16,56). These two proteins were chosen for study because they are encoded in complex loci that play important parts in virulence, the emm and FCT loci, respectively, and because M protein, in particular, is a major component of the S. pyogenes cell envelope (3,9,36). The roles of M protein and protein F for surface exposure of Slr were studied with the M6 system, in which single mutants, lacking either protein, and a double mutant were available (5,16).…”