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.

Authors: Stover, James S; Chowdhury, Goutam; Zang, Hong; Guengerich, F Peter; Rizzo, Carmelo J

Published In Chem Res Toxicol, (2006 Nov)

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.

PubMed ID: 17112239

MeSH Terms: Bacteria/genetics; Cooking; DNA Adducts/chemistry*; DNA Replication; DNA-Directed DNA Polymerase/chemistry*; DNA-Directed DNA Polymerase/genetics; Deoxyguanosine/chemistry*; Deoxyribonucleases, Type II Site-Specific/chemistry*; Gene Deletion; Hot Temperature; Molecular Structure; Mutagens/chemistry; Oligonucleotides/chemical synthesis; Oligonucleotides/chemistry*; Oligonucleotides/genetics; Prokaryotic Cells/enzymology; Quinolines/chemistry*