title: RecA-mediated excision repair: a novel mechanism for repairing DNA lesions at sites of arrested DNA synthesis.
abstract: In Escherichia coli, bulky DNA lesions are repaired primarily by nucleotide excision repair (NER). Unrepaired lesions encountered by DNA polymerase at the replication fork create a blockage which may be relieved through RecF-dependent recombination. We have designed an assay to monitor the different mechanisms through which a DNA polymerase blocked by a single AAF lesion may be rescued by homologous double-stranded DNA sequences. Monomodified single-stranded plasmids exhibit low survival in non-SOS induced E. coli cells; we show here that the presence of a homologous sequence enhances the survival of the damaged plasmid more than 10-fold in a RecA-dependent way. Remarkably, in an NER proficient strain, 80% of the surviving colonies result from the UvrA-dependent repair of the AAF lesion in a mechanism absolutely requiring RecA and RecF activity, while the remaining 20% of the surviving colonies result from homologous recombination mechanisms. These results uncover a novel mechanism - RecA-mediated excision repair - in which RecA-dependent pairing of the mono-modified single-stranded template with a complementary sequence allows its repair by the UvrABC excinuclease.
authors.affiliation: Dept. Intégrité du Génome de l'UMR 7175, CNRS, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard Sebastien Brant, BP 10413, F-67412 Illkirch-Cedex, France. bichara@esbs.u-strasbg.fr
authors.forename: Marc
authors.initials: M
authors.lastname: Bichara
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pinet
authors.forename: Iain B
authors.initials: IB
authors.lastname: Lambert
authors.forename: Robert P P
authors.initials: RP
authors.lastname: Fuchs
mesh_terms: D003470:Culture Media; D004249:DNA Damage; D004260:DNA Repair; D004269:DNA, Bacterial / Q000096:biosynthesis* / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D010957:Plasmids / Q000235:genetics; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism; D014169:Transformation, Bacterial
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC