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Regulation of transcription by SMU.1349, a TetR family regulator, in Streptococcus mutans.

ABSTRACT: The TetR family of transcriptional regulators is ubiquitous in bacteria, where it plays an important role in bacterial gene expression. Streptococcus mutans, a gram-positive pathogen considered to be the primary etiological agent in the formation of dental caries, encodes at least 18 TetR regulators. Here we characterized one such TetR regulator, SMU.1349, encoded by the TnSmu2 operon, which appeared to be acquired by the organism via horizontal gene transfer. SMU.1349 is transcribed divergently from the rest of the genes encoded by the operon. By the use of a transcriptional reporter system and semiquantitative reverse transcription-PCR (RT-PCR), we demonstrated that SMU.1349 activates the transcription of several genes that are encoded within the TnSmu2 operon. Gel mobility shift and DNase I footprinting assays with purified SMU.1349 protein demonstrated binding to the intergenic region between SMU.1349 and the TnSmu2 operon; therefore, SMU.1349 is directly involved in gene transcription. Using purified S. mutans RpoD and Escherichia coli RNA polymerase, we also demonstrated in an in vitro transcription assay that SMU.1349 could activate transcription from the TnSmu2 operon promoter. Furthermore, we showed that SMU.1349 could also repress transcription from its own promoter by binding to the intergenic region, suggesting that SMU.1349 acts as both an activator and a repressor. Thus, unlike most of the TetR family proteins, which generally function as transcriptional repressors, SMU.1349 is unique in that it can function as both.

SUBMITTER: Chattoraj P

PROVIDER: S-EPMC3232899 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Regulation of transcription by SMU.1349, a TetR family regulator, in Streptococcus mutans.

Chattoraj Partho P Mohapatra Saswat Sourav SS Rao J L Uma Maheswar JL Biswas Indranil I

Journal of bacteriology 20110930 23

The TetR family of transcriptional regulators is ubiquitous in bacteria, where it plays an important role in bacterial gene expression. Streptococcus mutans, a gram-positive pathogen considered to be the primary etiological agent in the formation of dental caries, encodes at least 18 TetR regulators. Here we characterized one such TetR regulator, SMU.1349, encoded by the TnSmu2 operon, which appeared to be acquired by the organism via horizontal gene transfer. SMU.1349 is transcribed divergently ...[more]

PMID: 21965566

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Project description:In Streptococcus mutans, SprV (SMU.2137) is a pleiotropic regulator that differentially regulates genes related to competence, mutacin production, biofilm formation, and the stress tolerance response, along with some other pathways. In this study, we established a link between SprV and an ∼67-kDa protein in the culture supernatant of strain UA159 that was later confirmed as SMU.63 by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. We discovered that SprV downregulates the transcription and translation of SMU.63. We found that the seven amino acids from the C-terminal region of SprV were also crucial for the expression of SMU.63. Deletion of smu.63 led to increased sucrose-independent biofilm formation and competence. The sprV deletion also increased biofilm formation although this could be partially attributed to the downregulation of smu.63 In an smu.63 sprV double mutant, a synergistic effect was observed in biofilm formation in contrast to effects on competence development. We found that low or excess magnesium ion repressed sprV transcription that, in turn, affected the expression of smu.63 As expected, a magnesium ion-dependent effect of competence and biofilm formation was observed in the UA159 strain. We also replicated the results of SMU.63 expression and competence in S. mutans GS5 that encodes both SprV and SMU.63 homologs and found that the GS5 strain behaves similarly to the UA159 strain, indicating that SprV's effect is strain independent.IMPORTANCE We previously identified a pleiotropic regulator, SprV, in Streptococcus mutans This regulator appears to be highly conserved among streptococci. Here, we showed that SprV regulates the expression of a secreted protein encoded by SMU.63 in S. mutans SMU.63 has been known to impact biofilm formation and genetic competence, two important characteristics that help in colonization of the organism. SMU.63 is also unique since it is known to form amyloid fiber. We found that SprV regulates the expression of SMU.63 at both the transcriptional and translational levels. We also found that the expression of SprV is regulated by magnesium ion concentration. Interestingly, both low and high magnesium ion concentrations affected biofilm formation and genetic competence. Since SMU.63 is also highly conserved among streptococci, we hypothesized that SprV will have a similar effect on its expression.

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Dataset Information

Regulation of transcription by SMU.1349, a TetR family regulator, in Streptococcus mutans.

Publications

Regulation of transcription by SMU.1349, a TetR family regulator, in Streptococcus mutans.

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