title: Genes on a Wire: The Nucleoid-Associated Protein HU Insulates Transcription Units in Escherichia coli.
abstract: The extent to which chromosomal gene position in prokaryotes affects local gene expression remains an open question. Several studies have shown that chromosomal re-positioning of bacterial transcription units does not alter their expression pattern, except for a general decrease in gene expression levels from chromosomal origin to terminus proximal positions, which is believed to result from gene dosage effects. Surprisingly, the question as to whether this chromosomal context independence is a cis encoded property of a bacterial transcription unit, or if position independence is a property conferred by factors acting in trans, has not been addressed so far. For this purpose, we established a genetic test system assessing the chromosomal positioning effects by means of identical promoter-fluorescent reporter gene fusions inserted equidistantly from OriC into both chromosomal replichores of Escherichia coli K-12. Our investigations of the reporter activities in mutant cells lacking the conserved nucleoid associated protein HU uncovered various drastic chromosomal positional effects on gene transcription. In addition we present evidence that these positional effects are caused by transcriptional activity nearby the insertion site of our reporter modules. We therefore suggest that the nucleoid-associated protein HU is functionally insulating transcription units, most likely by constraining transcription induced DNA supercoiling.
authors.affiliation: Institut für Hygiene, University Münster, Mendelstraße 7, 48149 Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Berger
authors.affiliation: School of Engineering and Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Veneta
authors.initials: V
authors.lastname: Gerganova
authors.affiliation: Institut für Hygiene, University Münster, Mendelstraße 7, 48149 Münster, Germany.
authors.forename: Petya
authors.initials: P
authors.lastname: Berger
authors.affiliation: School of Engineering and Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Radu
authors.initials: R
authors.lastname: Rapiteanu
authors.affiliation: School of Engineering and Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Viktoras
authors.initials: V
authors.lastname: Lisicovas
authors.affiliation: Institut für Hygiene, University Münster, Mendelstraße 7, 48149 Münster, Germany.|Interdisciplinary Center for Clinical Research (IZKF), University of Münster, Münster, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Dobrindt
mesh_terms: D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D051738:Origin Recognition Complex / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; C116822:hns protein, E coli