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J. Bacteriol. doi:10.1128/JB.01689-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The novel transcription factor SgrR coordinates the response to glucose-phosphate stress

Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD 20892

^* To whom correspondence should be addressed. Email: cvanderp{at}life.uiuc.edu.

	Abstract

SgrR is the first characterized member of a family of bacterial transcription factors containing an N-terminal DNA binding domain and C-terminal solute binding domain. Previously, we reported genetic evidence that SgrR activates the divergently transcribed gene, sgrS, which encodes a small RNA required for recovery from glucose-phosphate stress. In this study, we examined the regulation of sgrR expression and found that SgrR negatively autoregulates its own transcription in the presence and absence of stress. An SgrR binding site in the sgrR-sgrS intergenic region is required in vivo for both SgrR-dependent activation of sgrS and autorepression of sgrR. Purified SgrR binds specifically to sgrS promoter DNA in vitro; a mutation in the site required for in vivo activation and autorepression abrogates in vitro SgrR binding. A plasmid library screen identified clones that alter expression of a P_sgrS-lacZ fusion; some act by titrating endogenous SgrR. The yfdZ gene, encoding a putative aminotransferase, was identified in this screen; the yfdZ promoter contains an SgrR binding site, and transcriptional fusions indicate that yfdZ is activated by SgrR. Clones containing mlc, which encodes a glucose-specific repressor protein, also downregulate P_sgrS-lacZ. The mlc clones do not appear to titrate the SgrR protein, indicating that Mlc affects sgrS expression by an alternative mechanism.

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• Wadler, C. S., Vanderpool, C. K. (2007). From the Cover: A dual function for a bacterial small RNA: SgrS performs base pairing-dependent regulation and encodes a functional polypeptide. Proc. Natl. Acad. Sci. USA 104: 20454-20459 [Abstract] [Full Text]