Mutational Spectrum of N-hydroxy-N-acetyl-4-aminobiphenyl at Exon 3 of the HPRT Gene
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4-Aminobiphenyl is a human bladder carcinogen present in many environmental sources, including cigarette smoke. It can be metabolized in two steps to the mutagen N-hydroxy-N-acetyl-4-aminobiphenyl (N-OH-AABP). In this study the mutational spectrum of N-OH-AABP-exposed human lymphoblastoid cells (TK6) was deter- mined using HPRT as the target gene. Three large, HAT (hypoxanthine– aminopterin–thymidine)-cleaned TK6 cultures were independently treated with 20 m M N-OH-AABP for 24 h, allowed to recover for 4 days, then continuously exposed to 40 m M 6-thioguanine to select for induced mutants. Contemporary control cultures received vehicle in place of N-OH-AABP. N-OH-AABP treatment gave an 11-fold increase in mutation frequency. Mutations were delineated in exon 3 of the HPRT gene directly from genomic DNA extracted from both treated and untreated cells using the polymerase chain reaction, denaturing gradient gel electrophoresis (DGGE) and dideoxy sequencing. DGGE analysis showed N-OH-AABP increased both the number and type of mutations as compared with controls. The major background mutation was a G(197) to A transition. The major N-OH-AABP-induced changes were G(209-211) to T transversions (30%), a seven-base repeat at position 185 (17%) and an A(215) to T transversion (2%). Theshift in the control spectrum of a transition to that of transversions and insertions suggest that the electrophile N-OH-AABP forms bulky adducts at the same sites on exon 3 of HPRT as do many other bulky electrophiles, causes replication errors by similar mechanisms, but induces at least one potentially signature mutation.
Medical Specialties | Medicine and Health Sciences | Osteopathic Medicine and Osteopathy
Zayas-Rivera, Beatriz; Zhang, Lifang; Grant, Stephen G.; Keohavong, Phouthone; and Day, Billy W., "Mutational Spectrum of N-hydroxy-N-acetyl-4-aminobiphenyl at Exon 3 of the HPRT Gene" (2001). College of Osteopathic Medicine Faculty Articles. 1082.