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Identification of binding sites for the group A streptococcal global regulator CovR
Author(s) -
Federle Michael J.,
Scott June R.
Publication year - 2002
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 - 10.1046/j.1365-2958.2002.02810.x
Subject(s) - biology , operon , binding site , thymine , dna , streptococcus pyogenes , transcription (linguistics) , virulence , microbiology and biotechnology , promoter , transcription factor , dna binding site , genetics , gene , gene expression , bacteria , escherichia coli , staphylococcus aureus , linguistics , philosophy
Summary The CovRS two‐component system (also called CsrRS) of the group A streptococcus (GAS) acts as a global regulator, influencing the transcription of at least six virulence factors. The synthesis of the hyaluronic acid capsule, a virulence factor encoded by the hasABC operon, is negatively regulated by CovRS. We confirmed that phosphorylation of CovR increases its binding to a DNA fragment containing the hasA promoter. Using DNase I footprinting, we identified five binding sites surrounding the hasA promoter from bases –79 to + 73 (where + 1 is the start of transcription). One pair of thymines within each binding site appears to be necessary for CovR binding in vitro , as shown by uracil interference analysis. When each of these thymine pairs was altered by site‐directed mutagenesis, CovR binding was reduced in vitro , confirming the role of each thymine pair in binding. Using a transcriptional reporter system with a single chromosomal copy of P hasA–gusA , we demonstrated the importance of each of four of these binding sites for CovR repression of the hasA promoter. Based on this information, we propose a consensus sequence for CovR binding to DNA.