Fidelity of translesional synthesis past benzo[a]pyrene diol epoxide-2'-deoxyguanosine DNA adducts: marked effects of host cell, sequence context, and chirality.
We have used a site-specific approach to investigate the mutagenic potential of (+)- and (-)-trans-anti-benzo[a]pyrene diol epoxide (BPDE) DNA adducts. Oligodeoxyribonucleotides (5'TCCTCCTG1G2-CCTCTC), modified at the exocyclic amino groups of G1 or G2, were incorporated into a single-stranded shuttle vector and introduced into Escherichia coli or simian kidney (COS) cells. This experimental system permits translesional synthesis to proceed in the absence of DNA repair. The presence of (+)- or (-)-BPDE-N2-dG adducts strongly inhibited translesional synthesis in E. coli; induction of cellular SOS functions reduced this blocking effect. Vectors containing (+)-BPDE adducts at G1 or G2 generated mutation frequencies of 19% and 3%, respectively; these values were not altered significantly by induction of SOS functions. In COS cells, (+)-BPDE-modified vectors generated mutation frequencies of 13% at G1 and 45% at G2. In E. coli, the (-)-BPDE adduct generated mutation frequencies of < or = 2% at G1 and G2 and, in COS cells, 13% at G1 and 21% at G2. The predominant mutations in E. coli and COS cells were G-->T transversions targeted to the site of the lesion; however, when G2 was modified, a significant number of targeted G-->A and G-->C mutations were observed in COS cells. We conclude from this study that (+)-and (-)-BPDE-N2-dG adducts pair preferentially to dCMP and dAMP during translesional synthesis in a process that is strongly influenced by the stereochemistry of the adduct, by the bases flanking the lesion, and by host cell factors.
Moriya
M
M
Department of Pharmacological Sciences, State University of New York, Stony Brook 11794-8651, USA.
Spiegel
S
S
Fernandes
A
A
Amin
S
S
Liu
T
T
Geacintov
N
N
Grollman
A P
AP
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D018736:DNA Adducts / Q000737:chemistry / Q000378:metabolism*; D015342:DNA Probes / Q000235:genetics; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005822:Genetic Vectors; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D014170:Transformation, Genetic
D018736:DNA Adducts; D015342:DNA Probes; D009838:Oligodeoxyribonucleotides; C043931:benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-DNA; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide