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Journal of Bacteriology, January 2002, p. 126-133, Vol. 184, No. 1
0021-9193/01/$04.00+0     DOI: 10.1128/JB.184.1.126-133.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Analysis of cis- and trans-Acting Factors Involved in Regulation of the Streptococcus mutans Fructanase Gene (fruA)

Zezhang T. Wen and Robert A. Burne*

Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610

Received 11 June 2001/ Accepted 28 September 2001

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.


* Corresponding author. Mailing address: Department of Oral Biology, University of Florida, College of Dentistry, P.O. Box 100424, Gainesville, FL 32610. Phone: (352) 392-4370. Fax: (352) 392-7357. E-mail: rburne{at}dental.ufl.edu.


Journal of Bacteriology, January 2002, p. 126-133, Vol. 184, No. 1
0021-9193/01/$04.00+0     DOI: 10.1128/JB.184.1.126-133.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.




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