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RivR and the small RNA RivX: the missing links between the CovR regulatory cascade and the Mga regulon
Author(s) -
Roberts Samantha A.,
Scott June R.
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.06015.x
Subject(s) - regulon , biology , virulence , gene , plasmid , streptococcus pyogenes , genetics , transcription (linguistics) , locus (genetics) , transcription factor , regulation of gene expression , rna , sigma factor , rna polymerase , bacteria , linguistics , philosophy , staphylococcus aureus
Summary The CovR/S two‐component system regulates the transcription of many genes that are crucial for the virulence of Streptococcus pyogenes (group A Streptococcus , GAS). Previously, we demonstrated that one gene repressed directly by CovR is rivR , which encodes a member of the RofA‐like family of transcriptional regulators. In this study, we deleted rivR and its downstream gene rivX in a ΔcovR background. Microarray analysis revealed that the products of the rivRX locus exert positive control over the transcription of members of the Mga regulon. Using mutational analysis, we established that rivX encodes a small regulatory RNA. We found that RivR enhances transcriptional activation by Mga in vivo and in vitro . An M1 Δ covR Δ rivRX strain is attenuated for virulence in a murine model of invasive soft tissue infection and this attenuation is complemented by rivRX expressed from a plasmid, demonstrating the importance of the rivRX locus in pathogenesis. This study provides the first link between the CovR and Mga regulatory networks. By integrating the signals received through these two global regulators, GAS is able to select from its repertoire different combinations of specific virulence factors to express in response to a broad spectrum of environmental conditions.