title: Complex transcriptional and post-transcriptional regulation of an enzyme for lipopolysaccharide modification.
abstract: The PhoQ/PhoP two-component system activates many genes for lipopolysaccharide (LPS) modification when cells are grown at low Mg(2+) concentrations. An additional target of PhoQ and PhoP is MgrR, an Hfq-dependent small RNA that negatively regulates expression of eptB, also encoding a protein that carries out LPS modification. Examination of LPS confirmed that MgrR effectively silences EptB; the phosphoethanolamine modification associated with EptB is found in ΔmgrR::kan but not mgrR(+) cells. Sigma E has been reported to positively regulate eptB, although the eptB promoter does not have the expected Sigma E recognition motifs. The effects of Sigma E and deletion of mgrR on levels of eptB mRNA were independent, and the same 5' end was found in both cases. In vitro transcription and the behaviour of transcriptional and translational fusions demonstrate that Sigma E acts directly at the level of transcription initiation for eptB, from the same start point as Sigma 70. The results suggest that when Sigma E is active, synthesis of eptB transcript outstrips MgrR-dependent degradation; presumably the modification of LPS is important under these conditions. Adding to the complexity of eptB regulation is a second sRNA, ArcZ, which also directly and negatively regulates eptB.
authors: Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD 20892, USA.
authors: Kyung
authors: K
authors: Moon
authors: David A
authors: DA
authors: Six
authors: Hyun-Jung
authors: HJ
authors: Lee
authors: Christian R H
authors: CR
authors: Raetz
authors: Susan
authors: S
authors: Gottesman
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005786:Gene Expression Regulation; D008070:Lipopolysaccharides / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; C465562:PhoP protein, E coli; C576029:PhoQ protein, E coli; D034741:RNA, Small Interfering; D012808:Sigma Factor; C063202:sporulation-specific sigma factors; C501859:EptB protein, E coli; D017853:Phosphotransferases (Alcohol Group Acceptor)
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