title: The E. coli DNA Replication Fork.
abstract: DNA replication in Escherichia coli initiates at oriC, the origin of replication and proceeds bidirectionally, resulting in two replication forks that travel in opposite directions from the origin. Here, we focus on events at the replication fork. The replication machinery (or replisome), first assembled on both forks at oriC, contains the DnaB helicase for strand separation, and the DNA polymerase III holoenzyme (Pol III HE) for DNA synthesis. DnaB interacts transiently with the DnaG primase for RNA priming on both strands. The Pol III HE is made up of three subassemblies: (i) the αɛθ core polymerase complex that is present in two (or three) copies to simultaneously copy both DNA strands, (ii) the β2 sliding clamp that interacts with the core polymerase to ensure its processivity, and (iii) the seven-subunit clamp loader complex that loads β2 onto primer-template junctions and interacts with the α polymerase subunit of the core and the DnaB helicase to organize the two (or three) core polymerases. Here, we review the structures of the enzymatic components of replisomes, and the protein-protein and protein-DNA interactions that ensure they remain intact while undergoing substantial dynamic changes as they function to copy both the leading and lagging strands simultaneously during coordinated replication.
authors.affiliation: Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: J S
authors.initials: JS
authors.lastname: Lewis
authors.affiliation: Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Jergic
authors.affiliation: Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia. Electronic address: nickd@uow.edu.au.
authors.forename: N E
authors.initials: NE
authors.lastname: Dixon
mesh_terms: D004258:DNA Polymerase III / Q000378:metabolism; D019915:DNA Primase / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D019915:DNA Primase; D004258:DNA Polymerase III
keywords: Clamp loader; DNA polymerase III; DnaB helicase; DnaG primase; Lagging strand; Leading strand; Okazaki fragment; Sliding clamp