The major, N2-Gua adduct of the (+)-anti-benzo[a]pyrene diol epoxide is capable of inducing G-->A and G-->C, in addition to G-->T, mutations.
Mutations induced by the (+)-anti-diol epoxide of benzo[a]pyrene [(+)-anti-B[a]PDE] were collected in the supF gene of the Escherichia coli plasmid pUB3. pUB3 was reacted with (+)-anti-B[a]-PDE and then either (1) transformed immediately into E. coli or (2) heated at 80 degrees C for 10 min and then cooled prior to transformation--the latter to probe mechanism [Rodriguez & Loechler (1993) Biochemistry 32, 1759]. Qualitatively, heating did not affect the mutagenic pattern, except at the major base substitution hotspot in supF, G115, where principally G-->T mutations were obtained prior to heating, while after heating, G-->A and G-->C mutations became statistically significantly more prevalent. Several studies have suggested that a heat-induced chemical transformation of a (+)-anti-B[a]PDE adduct at G115 (e.g., into an apurinic site) is not likely to explain the change in mutational pattern. The most likely model is that (+)-anti-B[a]P-N2-Gua is initially trapped in a metastable conformation giving principally G-->T mutations, while heating induces a change to a stable conformation(s) resulting in G-->T, A, and C mutations. This suggests that adduct conformational complexity is at the root of adduct mutational complexity. To investigate this model, a plasmid (B[a]P-G115-pRE1) with (+)-anti-B[a]P-N2-Gua in the G115 sequence context is constructed using adduct site-specific techniques.(ABSTRACT TRUNCATED AT 250 WORDS)
Jelinsky
S A
SA
Department of Biology, Boston University, Massachusetts 02215, USA.
Liu
T
T
Geacintov
N E
NE
Loechler
E L
EL
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism* / Q000633:toxicity; D000225:Adenine; D001483:Base Sequence; D003596:Cytosine; D018736:DNA Adducts; D015252:Deoxyribonucleases, Type II Site-Specific; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D006147:Guanine; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009153:Mutagens / Q000378:metabolism* / Q000633:toxicity; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D017354:Point Mutation; D015183:Restriction Mapping; D013329:Structure-Activity Relationship; D013941:Thymine
D018736:DNA Adducts; D009153:Mutagens; D009838:Oligodeoxyribonucleotides; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D006147:Guanine; D003596:Cytosine; D015252:Deoxyribonucleases, Type II Site-Specific; C024400:GTYRAC-specific type II deoxyribonucleases; D000225:Adenine; D013941:Thymine