title: Mechanisms of transcription-replication collisions in bacteria.
abstract: While collisions between replication and transcription in bacteria are deemed inevitable, the fine details of the interplay between the two machineries are poorly understood. In this study, we evaluate the effects of transcription on the replication fork progression in vivo, by using electrophoresis analysis of replication intermediates. Studying Escherichia coli plasmids, which carry constitutive or inducible promoters in different orientations relative to the replication origin, we show that the mutual orientation of the two processes determines their mode of interaction. Replication elongation appears not to be affected by transcription proceeding in the codirectional orientation. Head-on transcription, by contrast, leads to severe inhibition of the replication fork progression. Furthermore, we evaluate the mechanism of this inhibition by limiting the area of direct contact between the two machineries. We observe that replication pausing zones coincide exactly with transcribed DNA segments. We conclude, therefore, that the replication fork is most likely attenuated upon direct physical interaction with the head-on transcription machinery.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S. Ashland Ave., Chicago, IL 60607, USA. mirkin@uic.edu
authors.forename: Ekaterina V
authors.initials: EV
authors.lastname: Mirkin
authors.forename: Sergei M
authors.initials: SM
authors.lastname: Mirkin
mesh_terms: D004261:DNA Replication / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D007544:Isopropyl Thiogalactoside / Q000737:chemistry; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D018741:Replication Origin / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D007544:Isopropyl Thiogalactoside