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Mutagenic specificity of the (+) anti ‐diol epoxide of dibenz[ a,j ]anthracene in the supF gene of an Escherichia coli plasmid
Author(s) -
Gill Rosalynn D.,
Digiovanni John,
Cortez Cecilia,
Harvey Ronald G.,
Rodriguez Henry,
Loechler Edward L.
Publication year - 1993
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/mc.2940080305
Subject(s) - biology , mutation frequency , plasmid , microbiology and biotechnology , escherichia coli , mutation , point mutation , shuttle vector , transition (genetics) , transversion , genetics , gene , vector (molecular biology) , recombinant dna
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 (Δ pro‐lac, strA )/F′( pro + , lacl Q , lacl am26 , lacZΔM 15 ). 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→ transitions were the major mutations observed in SOS‐induced cells (37%). GC→T́ (21%) and GC→C̀ (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→Ã/AT transition mutations were also observed (about 15% of all mutations in SOS‐induced cells). Taken together, single and tandem GC→Ã 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→Ã transitions.