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A secondary RNA polymerase sigma factor from Streptococcus pyogenes
Author(s) -
Opdyke Jason A.,
Scott June R.,
Moran Charles P.
Publication year - 2001
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.1365-2958.2001.02657.x
Subject(s) - sigma factor , biology , rna polymerase , transcription (linguistics) , general transcription factor , promoter , rna polymerase ii , microbiology and biotechnology , streptococcus pyogenes , rna polymerase ii holoenzyme , orfs , genetics , gene , rna , gene expression , open reading frame , bacteria , staphylococcus aureus , peptide sequence , linguistics , philosophy
The important human pathogen Streptococcus pyogenes (the group A streptococcus or GAS) causes diseases ranging from mild, self‐limiting pharyngitis to severe invasive infections. Regulation of the expression of GAS genes in response to specific environmental differences within the host is probably key in determining the course of the infectious process, however, little is known of global regulators of gene expression in GAS. Although secondary RNA polymerase sigma factors act as global regulators of gene expression in many other bacteria, none has yet been isolated from the GAS. The newly available GAS genome sequence indicates that the only candidate secondary sigma factor is encoded by two identical open reading frames (ORFS). These ORFS encode a protein that is 40% identical to the transcription factor ComX, believed to act as an RNA polymerase sigma factor in Streptococcus pneumoniae . To test whether the GAS ComX homologue functions as a sigma factor, we cloned and purified it from Escherichia coli . We found that in vitro, this GAS protein, which we call σ X , directed core RNA polymerase from Bacillus subtilis to transcribe from two GAS promoters that contain the cin‐box region, required for transcription by S. pneumoniae ComX in vivo . On the other hand, GAS σ X did not promote transcription of a GAS promoter ( hasA ) expected to be dependent on σ A , the housekeeping or primary RNA polymerase sigma factor. Addition of monoclonal antibody that inhibited σ A ‐directed transcription had no effect on σ X ‐directed transcription, showing that the latter was not the result of contaminating σ A . Transcription of both cin‐box‐containing promoters initiated downstream of the cin‐box and two different single basepair substitutions in the cin‐box of the cinA promoter each caused a severe reduction of σ X ‐directed transcription in vitro . Thus, the cin‐box is required for σ X ‐directed transcription.