title: Two mechanisms produce mutation hotspots at DNA breaks in Escherichia coli.
abstract: Mutation hotspots and showers occur across phylogeny and profoundly influence genome evolution, yet the mechanisms that produce hotspots remain obscure. We report that DNA double-strand breaks (DSBs) provoke mutation hotspots via stress-induced mutation in Escherichia coli. With tet reporters placed 2 kb to 2 Mb (half the genome) away from an I-SceI site, RpoS/DinB-dependent mutations occur maximally within the first 2 kb and decrease logarithmically to ∼60 kb. A weak mutation tail extends to 1 Mb. Hotspotting occurs independently of I-site/tet-reporter-pair position in the genome, upstream and downstream in the replication path. RecD, which allows RecBCD DSB-exonuclease activity, is required for strong local but not long-distance hotspotting, indicating that double-strand resection and gap-filling synthesis underlie local hotspotting, and newly illuminating DSB resection in vivo. Hotspotting near DSBs opens the possibility that specific genomic regions could be targeted for mutagenesis, and could also promote concerted evolution (coincident mutations) within genes/gene clusters, an important issue in the evolution of protein functions.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Chandan
authors.initials: C
authors.lastname: Shee
authors.forename: Janet L
authors.initials: JL
authors.lastname: Gibson
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D043211:Exodeoxyribonuclease V / Q000378:metabolism; D017930:Genes, Reporter; D009154:Mutation; D012808:Sigma Factor / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli