title: The Balance between Recombination Enzymes and Accessory Replicative Helicases in Facilitating Genome Duplication.
abstract: Accessory replicative helicases aid the primary replicative helicase in duplicating protein-bound DNA, especially transcribed DNA. Recombination enzymes also aid genome duplication by facilitating the repair of DNA lesions via strand exchange and also processing of blocked fork DNA to generate structures onto which the replisome can be reloaded. There is significant interplay between accessory helicases and recombination enzymes in both bacteria and lower eukaryotes but how these replication repair systems interact to ensure efficient genome duplication remains unclear. Here, we demonstrate that the DNA content defects of Escherichia coli cells lacking the strand exchange protein RecA are driven primarily by conflicts between replication and transcription, as is the case in cells lacking the accessory helicase Rep. However, in contrast to Rep, neither RecA nor RecBCD, the helicase/exonuclease that loads RecA onto dsDNA ends, is important for maintaining rapid chromosome duplication. Furthermore, RecA and RecBCD together can sustain viability in the absence of accessory replicative helicases but only when transcriptional barriers to replication are suppressed by an RNA polymerase mutation. Our data indicate that the minimisation of replisome pausing by accessory helicases has a more significant impact on successful completion of chromosome duplication than recombination-directed fork repair.
authors.affiliation: Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK. aisha.syeda@york.ac.uk.
authors.forename: Aisha H
authors.initials: AH
authors.lastname: Syeda
authors.affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. j.d.atkinson@gmx.com.
authors.forename: John
authors.initials: J
authors.lastname: Atkinson
authors.affiliation: Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK. bob.lloyd@nottingham.ac.uk.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Lloyd
authors.affiliation: Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK. peter.mcglynn@york.ac.uk.
authors.forename: Peter
authors.initials: P
authors.lastname: McGlynn
keywords: RNA polymerase; genome stability; repair; replication