Mutagenic specificity of the (+)anti-diol epoxide of dibenz[a,j]anthracene in the supF gene of an Escherichia coli plasmid.
This study was designed to examine the mutagenic specificity of (+)anti-dibenz[a,j]anthracene 3,4-diol-1,2-epoxide ((+)anti-DB[a,j]A-DE) in SOS-induced repair-proficient Escherichia coli ES87 (delta pro-lac, strA)/F' (pro+, lac1Q, lac1am26, lacZ delta M15). The plasmid pUB3, which contains the mutation target gene, supF, was modified with (+)anti-DB[a,j]A-DE in vitro (two to five adducts/plasmid) and then transformed into bacteria by electroporation. The spontaneous mutation frequency for unmodified pUB3 in uninduced cells was about 2 x 10(-6) and for SOS-induced cells, about 8 x 10(-6). The spontaneous supF- mutations were primarily insertions, deletions, and frameshifts. The mutation frequency for (+)anti-DB[a,j]A-DE-modified pUB3 was about 8 x 10(-6) and about 32 x 10(-6) for uninduced cells and SOS-induced cells, respectively. (+)anti-DB[a,j]A-DE induced primarily point mutations in supF in SOS-induced cells. GC-->AT transitions were the major mutations observed in SOS-induced cells (37%). GC-->TA (21%) and GC-->CG (8.6%) transversion mutations were also observed, whereas mutations at AT base pairs were rare (1.9%). Furthermore, a large number of tandem GC/GC-->AT/AT transition mutations were also observed (about 15% of all mutations in SOS-induced cells). Taken together, single and tandem GC-->AT mutations accounted for slightly over half (about 51%) of the mutations observed in SOS-induced cells. These results demonstrated that (+)anti-DB[a,j]A-DE was mutagenic in repair-proficient E. coli; however, unlike other polycyclic aromatic hydrocarbons that induce primarily transversion mutations, (+)anti-DB[a,j]A-DE caused mostly GC-->AT transitions.
Gill
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RD
University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, Smithville 78957.
Rodriguez
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H
Cortez
C
C
Harvey
R G
RG
Loechler
E L
EL
DiGiovanni
J
J
D001483:Base Sequence; D001551:Benz(a)Anthracenes / Q000494:pharmacology*; D018274:Electroporation; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009152:Mutagenicity Tests; D010957:Plasmids; D013014:SOS Response, Genetics
D001551:Benz(a)Anthracenes; C016365:dibenzanthracenes