Affiliation:
1. Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota 57069
Abstract
ABSTRACT
Streptococcus mutans
, the principal causative agent of dental caries, produces four glucan-binding proteins (Gbp) that play major roles in bacterial adherence and pathogenesis. One of these proteins, GbpC, is an important cell surface protein involved in biofilm formation. GbpC is also important for cariogenesis, bacteremia, and infective endocarditis. In this study, we examined the regulation of
gbpC
expression in
S. mutans
strain UA159. We found that
gbpC
expression attains the maximum level at mid-exponential growth phase, and the half-life of the transcript is less than 2 min. Expression from P
gbpC
was measured using a P
gbpC-gusA
transcriptional fusion reporter and was analyzed under various stress conditions, including thermal, osmotic, and acid stresses. Expression of
gbpC
is induced under conditions of thermal stress but is repressed during growth at low pH, whereas osmotic stress had no effect on expression from P
gbpC
. The results from the expression analyses were further confirmed using semiquantitative reverse transcription-PCR analysis. Our results also reveal that CovR, a global response regulator in many
Streptococcus
spp., represses
gbpC
expression at the transcriptional level. We demonstrated that purified CovR protein binds directly to the promoter region of P
gbpC
to repress
gbpC
expression. Using a DNase I protection assay, we showed that CovR binds to DNA sequences surrounding P
gbpC
from bases −68 to 28 (where base 1 is the start of transcription). In summary, our results indicate that various stress conditions modulate the expression of
gbpC
and that CovR negatively regulates the expression of the
gbpC
gene by directly binding to the promoter region.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
58 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献