Regulation of competence and gene expression in Streptococcus mutans by the RcrR transcriptional regulator

Summary An intimate linkage between the regulation of biofilm formation, stress tolerance and genetic competence exists in the dental caries pathogen Streptococcus mutans. The rcrRPQ genes encode ABC exporters (RcrPQ) and a MarR‐family transcriptional repressor of the rcr operon (RcrR) that play a d...

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Bibliographic Details
Published in:Molecular oral microbiology 2015-04, Vol.30 (2), p.147-159
Main Authors: Seaton, K., Ahn, S.-J., Burne, R.A.
Format: Article
Language:English
Subjects:
autolysis
Bacterial Proteins - genetics
Binding Sites
dental caries
Dentistry
DNA, Bacterial - genetics
DNA-Binding Proteins - genetics
Gene Expression Regulation, Bacterial
Genes, Reporter
genetic competence
Operon
peptide signalling
Promoter Regions, Genetic
Streptococcus mutans
Streptococcus mutans - genetics
Transcription, Genetic
transcriptional regulator
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Summary:Summary An intimate linkage between the regulation of biofilm formation, stress tolerance and genetic competence exists in the dental caries pathogen Streptococcus mutans. The rcrRPQ genes encode ABC exporters (RcrPQ) and a MarR‐family transcriptional repressor of the rcr operon (RcrR) that play a dominant role in the regulation of the development of genetic competence and connect competence with stress tolerance and (p)ppGpp production in S. mutans. Here we identify the target for efficient RcrR binding in the rcr promoter region using purified recombinant RcrR (rRcrR) protein in electrophoretic mobility shift assays and show that DNA fragments carrying mutations in the binding region were not bound as efficiently by rRcrR in vitro. Mutations in the RcrR binding site impacted expression from the rcrR promoter in vivo and elicited changes in transformation efficiency, competence gene expression, and growth inhibition by competence‐stimulating peptide; even when the changes in rcrRPQ transcription were minor. An additional mechanistic linkage of RcrR with competence and (p)ppGpp metabolism was identified by showing that the rRcrR protein could bind to the promoter regions of comX, comYA and relP, although the binding was not as efficient as to the rcrRPQ promoter under the conditions tested. Hence, tightly controlled autogenous regulation of the rcrRPQ operon by RcrR binding to specific target sites is essential for cellular homeostasis, and RcrR contributes to the integration of genetic competence, (p)ppGpp metabolism, and acid and oxidative stress tolerance in S. mutans through both direct and indirect mechanisms.
ISSN:2041-1006
2041-1014
DOI:10.1111/omi.12079