title: Complex transcriptional organization regulates an Escherichia coli locus implicated in lipopolysaccharide biogenesis.
abstract: The Escherichia coli yrbG-lptB locus (yrbG kdsD kdsC lptC lptA lptB) encodes genes for outer membrane biogenesis, namely, kdsC and kdsD for biosynthesis of the lipopolysaccharide inner core sugar Kdo, and lptA, lptB, and lptC for lipopolysaccharide transport to the outer membrane. Three promoters (yrbGp, kdsCp and the σ(E)-dependent lptAp) have been previously identified by genetic analysis. In this work, we show that transcription of this locus generates an array of overlapping mRNAs and we characterize the two intralocus promoter regions. In the kdsCp region, we identified three promoters (kdsCp1, kdsCp2, and kdsCp3) scattered within about 600 nt in the 3'-coding region of kdsD. The lptAp region is composed of two closely spaced promoters, lptAp1 and lptAp2. The former had been previously identified as a σ(E)-dependent promoter. Interestingly, lptAp1 is not activated by several stressful conditions that normally induce the σ(E)-dependent envelope stress response, whereas it seems to respond to conditions affecting lipopolysaccharide biogenesis, thus implying a specialized σ(E)-dependent LPS stress signaling pathway.
authors.affiliation: Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, 20133 Milan, Italy. alessandra.martorana@unimib.it
authors.forename: Alessandra M
authors.initials: AM
authors.lastname: Martorana
authors.forename: Paola
authors.initials: P
authors.lastname: Sperandeo
authors.forename: Alessandra
authors.initials: A
authors.lastname: Polissi
authors.forename: Gianni
authors.initials: G
authors.lastname: Dehò
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides