title: Translesion synthesis past the C8- and N2-deoxyguanosine adducts of the dietary mutagen 2-Amino-3-methylimidazo[4,5-f]quinoline in the NarI recognition sequence by prokaryotic DNA polymerases.
abstract: 2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) is found in cooked meats and forms DNA adducts at the C8- and N2-positions of dGuo after appropriate activation. IQ is a potent inducer of frameshift mutations in bacteria and is carcinogenic in laboratory animals. We have incorporated both IQ-adducts into the G1- and G3-positions of the NarI recognition sequence (5'-G1G2CG3CC-3'), which is a hotspot for arylamine modification. The in vitro replication of the oligonucleotides was examined with Escherichia coli pol I Klenow fragment exo-, E. coli pol II exo-, and Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4), and the extension products were sequenced by tandem mass spectrometry. Replication of the C8-adduct at the G3-position resulted in two-base deletions with all three polymerases, whereas error-free bypass and extension was observed at the G1-position. The N2-adduct was bypassed and extended by all three polymerases when positioned at the G1-position, and the error-free product was observed. The N2-adduct at the G3-position was more blocking and was bypassed and extended only by Dpo4 to produce an error-free product. These results indicate that the replication of the IQ-adducts of dGuo is strongly influenced by the local sequence and the regioisomer of the adduct. These results also suggest a possible role for pol II and IV in the error-prone bypass of the C8-IQ-adduct leading to frameshift mutations in reiterated sequences, whereas noniterated sequences result in error-free bypass.
authors.affiliation: Department of Chemistry, Center in Molecular Toxicology, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235-1822, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Stover
authors.forename: Goutam
authors.initials: G
authors.lastname: Chowdhury
authors.forename: Hong
authors.initials: H
authors.lastname: Zang
authors.forename: F Peter
authors.initials: FP
authors.lastname: Guengerich
authors.forename: Carmelo J
authors.initials: CJ
authors.lastname: Rizzo
mesh_terms: D001419:Bacteria / Q000235:genetics; D003296:Cooking; D018736:DNA Adducts / Q000737:chemistry*; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics; D003849:Deoxyguanosine / Q000737:chemistry*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry*; D017353:Gene Deletion; D006358:Hot Temperature; D015394:Molecular Structure; D009153:Mutagens / Q000737:chemistry; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry* / Q000235:genetics; D011387:Prokaryotic Cells / Q000201:enzymology; D011804:Quinolines / Q000737:chemistry*
chemical_list: D018736:DNA Adducts; D009153:Mutagens; D009841:Oligonucleotides; D011804:Quinolines; C029216:2-amino-3-methylimidazo(4,5-f)quinoline; D004259:DNA-Directed DNA Polymerase; D015252:Deoxyribonucleases, Type II Site-Specific; C046719:GGCGCC-specific type II deoxyribonucleases; D003849:Deoxyguanosine