Mutational specificity of the carcinogen 3-amino-1-methyl-5H-pyrido[4,3-b]-indole in mammalian cells.
We have used the pZipHprtNeo shuttle vector to determine the types of DNA sequence alterations induced by a potent carcinogen 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2). The shuttle vector contains a human cDNA hprt as the target gene and is stably integrated into a chromosome of the mouse cell line VH12. After Trp-P2 treatment, 59 independent HPRT- mutant clones of VH12 were isolated and altered sequences of the mutant hprt- cDNA genes were determined. Mutations induced by Trp-P2 comprised a variety of events; base substitutions, frameshifts, deletions and complex. Frameshifts were the most frequent mutational events (51%), and base substitutions were the next most frequent (30%) followed by deletions (14%). Examination of the DNA sequence context in the mutant genes revealed that approximately 70% of mutations induced by Trp-P2 occurred at G:C sites and thymine residues were the suggested target for the remainder of mutations. The results seem consistent with the previously reported finding that in vivo, metabolically activated Trp-P2 specifically binds to the C8 position of guanine residues in DNA to form C8G-Trp-P2 adducts (Hashimoto et al., Mutat, Res., 105, 9-13, 1982). As for molecular mechanisms, we showed that slippage and slippage misalignment could predict the generation of a large portion of Trp-P2-induced mutations found in the cDNA gene.
Akagi
T
T
Department of Fundamental Radiology, Osaka University, Medical School, Japan.
Morota
K
K
Iyehara-Ogawa
H
H
Kimura
H
H
Kato
T
T
D000818:Animals; D001483:Base Sequence; D002243:Carbolines / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002417:Cattle; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics; D004249:DNA Damage; D005796:Genes / Q000187:drug effects; D006147:Guanine / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D013866:Thioguanine / Q000494:pharmacology; D013941:Thymine / Q000502:physiology
D002243:Carbolines; D002273:Carcinogens; D006147:Guanine; C019133:3-amino-1-methyl-5H-pyrido(4,3-b)indole; D004247:DNA; D013866:Thioguanine; D013941:Thymine