DNA damage and mutations produced by chloroacetaldehyde in a CpG-methylated target gene.
Chloroacetaldehyde (CAA) is a metabolite of the human carcinogen vinyl chloride. CAA produces several types of DNA adducts including the exocyclic base adducts 3,N(4)-ethenocytosine, 1,N(6)-ethenoadenine, N(2),3-ethenoguanine, and 1,N(2)-ethenoguanine. Adducts of CAA with 5-methylcytosine have not yet been characterized. Here we have analyzed the mutational spectra produced by CAA in the supF gene of the pSP189 shuttle vector when present in either an unmethylated or CpG-methylated state. The vectors were replicated in human nucleotide excision repair-deficient XP-A fibroblasts. The mutational spectra obtained with the unmethylated and methylated supF target genes were generally similar with a preponderance of C/G to T/A transitions and C/G to A/T transversions. CAA-induced DNA adducts were mapped along the supF gene by using thermostable thymine DNA glycosylase (TDG) in conjunction with ligation-mediated PCR or by a Taq polymerase stop assay. Prominent CAA-induced TDG-sensitive sites were seen at several CpG positions but were independent of methylation. Methylated CpG sites were sites of CAA-induced mutations but were not the major mutational hotspots. Taq polymerase arrest sites were observed at numerous sequence positions in the supF gene and reflected the rather broad distributions of mutations along the sequence. We conclude that methylated CpG sites are not preferential targets for chloroacetaldehyde-induced mutagenesis.
Choi
Jun-Hyuk
JH
Division of Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
Pfeifer
Gerd P
GP
D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000633:toxicity*; D001483:Base Sequence; D002460:Cell Line; D018899:CpG Islands / Q000235:genetics; D018736:DNA Adducts / Q000032:analysis*; D004249:DNA Damage; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D017931:DNA Primers; D016153:Genes, Suppressor; D005822:Genetic Vectors; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D012343:RNA, Transfer / Q000235:genetics*; D019914:Taq Polymerase; D044502:Thymine DNA Glycosylase; D014162:Transfection
D018736:DNA Adducts; D017931:DNA Primers; C096275:supF tRNA; D012343:RNA, Transfer; C004656:chloroacetaldehyde; D019914:Taq Polymerase; D044502:Thymine DNA Glycosylase; D000079:Acetaldehyde