title: Replication fork reactivation downstream of a blocked nascent leading strand.
abstract: Unrepaired lesions in the DNA template pose a threat to accurate replication. Several pathways exist in Escherichia coli to reactivate a blocked replication fork. The process of recombination-dependent restart of broken forks is well understood, but the consequence of replication through strand-specific lesions is less well known. Here we show that replication can be restarted and leading-strand synthesis re-initiated downstream of an unrepaired block to leading-strand progression, even when the 3'-OH of the nascent leading strand is unavailable. We demonstrate that the loading by a replication restart system of a single hexamer of the replication fork helicase, DnaB, on the lagging-strand template is sufficient to coordinate priming by the DnaG primase of both the leading and lagging strands. These observations provide a mechanism for damage bypass during fork reactivation, demonstrate how daughter-strand gaps are generated opposite leading-strand lesions during the replication of ultraviolet-light-irradiated DNA, and help to explain the remarkable speed at which even a heavily damaged DNA template is replicated.
authors.affiliation: Molecular Biology Program, Weill Graduate School of Medical Sciences of Cornell University, New York, New York 10021, USA.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Heller
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Marians
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001710:Biotin / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis* / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism; D019915:DNA Primase / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication / Q000502:physiology*; D053488:DnaB Helicases; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D008957:Models, Genetic; D013698:Templates, Genetic
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C069995:PriC protein, E coli; D001710:Biotin; D004247:DNA; D019915:DNA Primase; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C121791:dnaG protein, E coli; D000251:Adenosine Triphosphatases; C506730:dnaB protein, E coli; D004265:DNA Helicases; D053488:DnaB Helicases