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首页> 外文期刊>Journal of bacteriology >Analysis of cis- and trans-Acting Factors Involved in Regulation of the Streptococcus mutans Fructanase Gene (fruA)
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Analysis of cis- and trans-Acting Factors Involved in Regulation of the Streptococcus mutans Fructanase Gene (fruA)

机译：变形链球菌果聚糖酶基因（fruA）调控中的顺式和反式作用因子分析

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There are two primary levels of control of the expression of the fructanase gene (fruA) of Streptococcus mutans: induction by levan, inulin, or sucrose and repression in the presence of glucose and other readily metabolized sugars. The goals of this study were to assess the functionality of putative cis-acting regulatory elements and to begin to identify the trans-acting factors involved in induction and catabolite repression of fruA. The fruA promoter and its derivatives generated by deletions and/or site-directed mutagenesis were fused to a promoterless chloramphenicol acetyltransferase (CAT) gene as a reporter, and strains carrying the transcriptional fusions were then analyzed for CAT activities in response to growth on various carbon sources. A dyadic sequence, ATGACA(TC)TGTCAT, located at ?72 to ?59 relative to the transcription initiation site was shown to be essential for expression of fruA. Inactivation of the genes that encode fructose-specific enzymes II resulted in elevated expression from the fruA promoter, suggesting negative regulation of fruA expression by the fructose phosphotransferase system. Mutagenesis of a terminator-like structure located in the 165-base 5′ untranslated region of the fruA mRNA or insertional inactivation of antiterminator genes revealed that antitermination was not a mechanism controlling induction or repression of fruA, although the untranslated leader mRNA may play a role in optimal expression of fructanase. Deletion or mutation of a consensus catabolite response element alleviated glucose repression of fruA, but interestingly, inactivation of the ccpA gene had no discernible effect on catabolite repression of fruA. Accumulating data suggest that expression of fruA is regulated by a mechanism that has several unique features that distinguish it from archetypical polysaccharide catabolic operons of other gram-positive bacteria.
机译：变形链球菌的果聚糖酶基因（ fruA ）表达的控制主要有两个水平：莱文，菊粉或蔗糖诱导和葡萄糖存在下的抑制和其他容易代谢的糖。这项研究的目的是评估推定的顺式调节元件的功能，并开始鉴定参与的诱导和分解代谢抑制的反式作用因子。 > fruA。通过缺失和/或定点诱变生成的 fruA 启动子及其衍生物与作为报告基因的无启动子氯霉素乙酰转移酶（CAT）基因融合，并携带转录的菌株然后分析融合物中的CAT活性，以响应各种碳源上的生长。二进序列ATGACA（TC）TGTCAT，位于相对于转录起始位点的第72至第59位，对表达 fruA 是必不可少的。果糖特异性酶II编码基因的失活导致 fruA 启动子的表达升高，表明果糖磷酸转移酶系统对 fruA 表达的负调控。位于 fruA mRNA 165个碱基的5'非翻译区的终止子样结构的诱变或抗终止子基因的插入失活表明，抗终止不是控制 fruA诱导或抑制的机制，尽管未翻译的前导mRNA可能在果糖酶的最佳表达中起作用。共有分解代谢物反应元件的缺失或突变减轻了 fruA 的葡萄糖抑制，但是有趣的是， ccpA 基因的失活对 fruA < / em>。越来越多的数据表明， fruA 的表达受一种机制调节，该机制具有几个独特的功能，可将其与其他革兰氏阳性细菌的典型多糖分解代谢操纵子区分开。

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