title: Characterization of the mutagenic spectrum of 4-nitroquinoline 1-oxide (4-NQO) in Aspergillus nidulans by whole genome sequencing.
abstract: 4-Nitroquinoline 1-oxide (4-NQO) is a highly carcinogenic chemical that induces mutations in bacteria, fungi, and animals through the formation of bulky purine adducts. 4-NQO has been used as a mutagen for genetic screens and in both the study of DNA damage and DNA repair. In the model eukaryote Aspergillus nidulans, 4-NQO-based genetic screens have been used to study diverse processes, including gene regulation, mitosis, metabolism, organelle transport, and septation. Early work during the 1970s using bacterial and yeast mutation tester strains concluded that 4-NQO was a guanine-specific mutagen. However, these strains were limited in their ability to determine full mutagenic potential, as they could not identify mutations at multiple sites, unlinked suppressor mutations, or G:C to C:G transversions. We have now used a whole genome resequencing approach with mutant strains generated from two independent genetic screens to determine the full mutagenic spectrum of 4-NQO in A. nidulans. Analysis of 3994 mutations from 38 mutant strains reveals that 4-NQO induces substitutions in both guanine and adenine residues, although with a 19-fold preference for guanine. We found no association between mutation load and mutagen dose and observed no sequence bias in the residues flanking the mutated purine base. The mutations were distributed randomly throughout most of the genome. Our data provide new evidence that 4-NQO can potentially target all base pairs. Furthermore, we predict that current practices for 4-NQO-induced mutagenesis are sufficient to reach gene saturation for genetic screens with feasible identification of causative mutations via whole genome resequencing.
authors.affiliation: Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Downes
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Mark
authors.initials: M
authors.lastname: Chonofsky
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115 Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China.
authors.forename: Kaeling
authors.initials: K
authors.lastname: Tan
authors.affiliation: Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Pfannenstiel
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Samara L
authors.initials: SL
authors.lastname: Reck-Peterson
authors.affiliation: Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506 rbtodd@k-state.edu.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Todd
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000737:chemistry / Q000633:toxicity*; D000225:Adenine / Q000737:chemistry; D001233:Aspergillus nidulans / Q000187:drug effects* / Q000235:genetics*; D004249:DNA Damage / Q000235:genetics; D016681:Genome, Fungal / Q000187:drug effects*; D006147:Guanine / Q000737:chemistry; D059014:High-Throughput Nucleotide Sequencing; D016296:Mutagenesis / Q000187:drug effects*; D010641:Phenotype; D017354:Point Mutation; D017422:Sequence Analysis, DNA
chemical_list: D015112:4-Nitroquinoline-1-oxide; D006147:Guanine; D000225:Adenine
keywords: 4-nitroquinoline 1-oxide; chemical mutagenesis; filamentous fungi; genetic screen; whole genome sequencing