Dose-dependent Differences in the Profile of Mutations Induced by (+)-7R,8S-Dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene in the Coding Region of the Hypoxanthine (Guanine) Phosphoribosyltransferase Gene in Chinese Hamster V-79 Cells

摘要: Chinese hamster V-79 cells were exposed to a high dose (0.30–0.48 µm; 32% cell survival), an intermediate (0.04–0.10 100% survival) or low (0.01–0.02 97% of (+)-7 R ,8 S -dihydroxy-9 ,10 -epoxy-7,8,9,10-tetrahydrobenzo( )pyrene [(+)-BPDE] which is the ultimate carcinogenic metabolite benzo( )pyrene. The mutation frequency for treated with dimethyl sulfoxide vehicle low, doses (+)-BPDE 1, 10, 52 514 8-azaguanine-resistant colonies/105 survivors, respectively. Independent clones isolated, and complementary DNAs prepared by reverse transcription. coding region hypoxanthine (guanine) phosphoribosyltransferase ( HPRT ) gene was amplified polymerase chain reaction sequenced. Altogether, 368 (+)-BPDE-induced mutant examined. At all doses, base substitutions most prevalent mutations observed (about 72% clones), followed exon deletions 26% clones) frame-shift 6% clones). cytotoxic dose, 7 120 occurred at AT pairs (6%) 113 GC (94%). noncytotoxic 20 82 (24%) 62 (76%). 27 76 (36%) 49 (64%). results indicated that decreasing decreased proportion increased pairs. As decreased, there dose-dependent decrease in GC→TA transversions (from 69% 42% substitutions) increase AT→CG 1% 25% substitutions). data also differences hot spots pairs. Although more than 99% guanine on nontranscribed strand DNA, adenine both transcribed strands. ratio 35:19 (+)-BPDE-treated cells. These observations suggest different mechanisms induction and/or repair premutagenic lesions Several nucleotide sequences frequent targeted guanines identified. included AGGGGGGC, TGGA, AGGA, TGGT, AGGC, TGGGA, AGGGA, TGGGGA. Seventy % substitution these sequences. ras motifs (corresponding codons 12, 13, 61) commonly chance.