%0 Journal Article
%T Multiple Roles for the sRNA GcvB in the Regulation of Slp Levels in Escherichia coli
%A Lorraine T. Stauffer
%A George V. Stauffer
%J ISRN Bacteriology
%D 2013
%R 10.1155/2013/918106
%X The Escherichia coli gcvB gene encodes a small RNA that regulates many genes involved in the transport of dipeptides, oligopeptides, and amino acids (oppA, dppA, cycA, and sstT). A microarray analysis of RNA isolated from an E. coli wild-type and a ¦¤gcvB strain grown to midlog phase in Luria-Bertani broth indicated that genes not involved in transport are also regulated by GcvB. One gene identified was slp that encodes an outer membrane lipoprotein of unknown function induced when cells enter stationary phase. The aim of this study was to verify that slp is a new target for GcvB-mediated regulation. In this study we used RT-PCR to show that GcvB regulates slp mRNA levels. GcvB negatively controls slp::lacZ in cells grown in Luria-Bertani broth by preventing an Hfq-mediated activation mechanism for slp::lacZ expression. In contrast, in glucose minimal medium supplemented with glycine, GcvB is required for inhibition of slp::lacZ expression, and Hfq prevents GcvB-mediated repression. Thus, GcvB regulates slp in both LB and in glucose minimal + glycine media and likely by mechanisms different than how it regulates sstT, dppA, cycA, and oppA. Repression of slp by GcvB results in an increase in resistance to chloramphenicol, and overexpression of slp in a ¦¤gcvB strain results in an increase in sensitivity to chloramphenicol. 1. Introduction The E. coli chromosome encodes ~100 small non-translated regulatory RNAs (sRNAs) [1]. A number of these sRNAs have been shown to function as regulators of outer membrane proteins and therefore play important roles in stress responses and virulence gene regulation [2¨C4]. In addition, most of these sRNAs regulate expression of target genes posttranscriptionally by base pairing with the target mRNAs [5]. The Hfq protein is required for regulation by this class of sRNAs [6]. In most cases, base pairing results in negative regulation of translational activity and altered stability of the target mRNA [5]. However, DsrA and RprA bind to rpoS mRNA, likely preventing formation of an inhibitory secondary structure that sequesters the ribosome-binding site, resulting in increased translation [7¨C9]. The gcvB gene encodes a nontranslated RNA of 206 nucleotides (nts) [10]. Transcription of the gcvB gene is activated by the GcvA protein when the cellular level of glycine is high and repressed by GcvA when the cellular level of glycine is limiting; repression requires an additional protein GcvR [10]. The production of GcvB is highest during the log phase of growth, and GcvB is not detectable in stationary phase cells [12]. In E. coli,
%U http://www.hindawi.com/journals/isrn.bacteriology/2013/918106/