Activation of the SMU.1882 transcription by CovR in Streptococcus mutans.
Activation of the SMU.1882 transcription by CovR in Streptococcus mutans.
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DOI：
10.1371/journal.pone.0015528
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发表时间：
2010-11-22
期刊：
影响因子：
3.7
通讯作者：
Biswas I
中科院分区：
文献类型：
--
作者：
Chong P;Chattoraj P;Biswas I
在变形链球菌中，全局反应调节因子CovR在生物膜形成、应激耐受反应和龋齿产生中起重要作用。我们以前已经表明，CovR作为一个转录抑制剂结合到其靶基因的上游启动子区。在这里，我们报告说，在体内，CovR激活SMU.1882，它编码一个小肽含有双甘氨酸基序的转录。我们还表明，SMU.1882是转录连接到comA编码一个假定的ABC转运蛋白。SMU.1882 -comA基因两侧有几个来自人类基因簇的编码甘露糖磷酸转移酶系统的基因。与其他链球菌的基因组比较表明SMU.1882是唯一存在于S.变形链球菌，而人操纵子是保守的所有链球菌，这表明可能发生了遗传重排在这个位点。通过使用转录报告系统和半定量RT-PCR，我们证明了SMU.1882的转录调控CovR。用纯化的CovR进行的体外凝胶位移和DNA酶I足迹分析表明，CovR与P1882的-10区域周围的大区域结合。利用这些信息，并与其他CovR调控的启动子相比，我们已经开发了一个推定的CovR的共识结合序列。尽管CovR与P1882结合，但使用纯化的S. mutans RpoD、E. coli RNA聚合酶，CovR不激活该启动子的转录。因此，我们推测在体内，CovR可能会干扰阻遏物的结合或需要辅因子。
In Streptococcus mutans, the global response regulator CovR plays an important role in biofilm formation, stress-tolerance response, and caries production. We have previously shown that CovR acts as a transcriptional repressor by binding to the upstream promoter regions of its target genes. Here, we report that in vivo, CovR activates the transcription of SMU.1882, which encodes a small peptide containing a double-glycine motif. We also show that SMU.1882 is transcriptionally linked to comA that encodes a putative ABC transporter protein. Several genes from man gene clusters that encode mannose phosphotranferase system flank SMU.1882 -comA genes. Genomic comparison with other streptococci indicates that SMU.1882 is uniquely present in S. mutans, while the man operon is conserved among all streptococci, suggesting that a genetic rearrangement might have taken place at this locus. With the use of a transcriptional reporter system and semi-quantitative RT-PCR, we demonstrated the transcriptional regulation of SMU.1882 by CovR. In vitro gel shift and DNase I foot-printing analyses with purified CovR suggest that CovR binds to a large region surrounding the -10 region of the P1882. Using this information and comparing with other CovR regulated promoters, we have developed a putative consensus binding sequence for CovR. Although CovR binds to P1882, in vitro experiments using purified S. mutans RpoD, E. coli RNA polymerase, and CovR did not activate transcription from this promoter. Thus, we speculate that in vivo, CovR may interfere with the binding of a repressor or requires a cofactor.
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