Role of the sRNA GcvB in regulation of cycA in Escherichia coli

Abstract

InEscherichia coli, thegcvBgene encodes a small non-translated RNA that regulates several genes involved in transport of amino acids and peptides (includingsstT,oppAanddppA). Microarray analysis identifiedcycAas an additional regulatory target of GcvB. ThecycAgene encodes a permease for the transport of glycine,d-alanine,d-serine andd-cycloserine. RT-PCR confirmed that GcvB and the Hfq protein negatively regulatecycAmRNA in cells grown in Luria–Bertani broth. In addition, deletion of thegcvBgene resulted in increased sensitivity tod-cycloserine, consistent with increased expression ofcycA. AcycA : : lacZtranslational fusion confirmed that GcvB negatively regulatescycAexpression in Luria–Bertani broth and that Hfq is required for the GcvB effect. GcvB had no effect oncycA : : lacZexpression in glucose minimal medium supplemented with glycine. However, Hfq still negatively regulated the fusion in the absence of GcvB. A set of transcriptional fusions ofcycAtolacZidentified a sequence incycAnecessary for regulation by GcvB. Analysis of GcvB identified a region complementary to this region ofcycAmRNA. However, mutations predicted to disrupt base-pairing betweencycAmRNA and GcvB did not alter expression ofcycA : : lacZ. A model for GcvB function in cell physiology is discussed.