Differences between the mutational consequences of replication of cis- and trans-opened benzo[a]pyrene 7,8-diol 9,10-epoxide-deoxyguanosine adducts in M13mp7L2 constructs.
The four adducts at N(2) of deoxyguanosine derived from cis-opening at C-10 of four optically active isomers of 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene were incorporated into 5'-TTCGAATCCTTCCCCC [context III(G)] and 5'-GGGGTTCCCGAGCGGC [context IV(G)] at the underlined site. The mutagenic consequences of these lesions in each of the two sequence contexts were examined after ligation of the modified oligonucleotides into single-stranded M13mp7L2 and replication of the vector in SOS-induced Escherichia coli. Total frequencies of base substitution mutations ranged between 14 and 48%. The mutation frequencies were generally higher in context IV(G) than in context III(G), and consisted mainly of G-->T followed by G-->C base substitutions. A substantial number of deletions or insertions of one guanine was also found for all adducts in context IV(G), where the adduct is located at the 3'-end of a run of five guanines. The overall frequencies of base substitution mutations induced by cis-opened adducts were substantially higher than those observed with the trans-opened dGuo adducts in the same sequences [Page et al. (1998) Biochemistry 37, 9127-9137]. Although G-->T base substitutions predominated for both the cis- and trans-opened adducts, the cis-opened dGuo adducts generally resulted in a higher proportion of G-->C [particularly in context III(G)] relative to G-->A, whereas the opposite was true for the trans-opened dGuo adducts. The present results along with previous data indicate that mutagenicity is highly dependent on a combination of sequence context and adduct stereochemistry.
Pontén
I
I
Chemistry of Carcinogenesis Laboratory, National Cancer Institute-Frederick, Frederick, Maryland 21702, USA.
Kroth
H
H
Sayer
J M
JM
Dipple
A
A
Jerina
D M
DM
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000009:adverse effects* / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001564:Benzo(a)pyrene / Q000009:adverse effects* / Q000737:chemistry; D002273:Carcinogens / Q000009:adverse effects* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts; D003849:Deoxyguanosine / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007536:Isomerism; D008969:Molecular Sequence Data; D009152:Mutagenicity Tests; D014162:Transfection
D002273:Carcinogens; D018736:DNA Adducts; D001564:Benzo(a)pyrene; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D003849:Deoxyguanosine