tx0601455_si_001.pdf (4.09 MB)
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
journal contribution
posted on 2006-11-20, 00:00 authored by James S. Stover, Goutam Chowdhury, Hong Zang, F. Peter Guengerich, Carmelo J. Rizzo2-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.