Splicing mutations in the CHO DHFR gene preferentially induced by (+/-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene.
AUTOR(ES)
Carothers, A M
RESUMO
Cultured Chinese hamster ovary (CHO) cells were treated with the polycyclic aromatic hydrocarbon racemic 3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene. Mutants deficient in dihydrofolate reductase activity were isolated. A carcinogen treatment at 0.1 microM yielded at 46% survival of the treated population and an induced frequency of mutation of 1.7 x 10(-4), 10(3)-fold greater than the spontaneous rate. By polymerase chain reaction amplification and direct DNA sequencing, we determined the base changes in 38 mutants. Base substitutions accounted for 78% (30/38) of the mutations. We obtained, in addition, four frameshift and four complex mutations. The preferred type of mutation was transversion (A.T----T.A and G.C----T.A) occurring in 69% of the analyzed mutants. A purine was on the 3' side of the putative adduct site in every mutant. Mutations were favored at sequences AGG, CAG, and AAG (the underlined base is the target). Surprisingly, 42% of the mutations created mRNA splicing defects (16/38), especially at splice acceptor sites for each of the five introns. Thus, this chemical carcinogen may recognize some aspect of DNA structure in regions corresponding to pre-mRNA splice sites.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=54345Documentos Relacionados
- DNA strand-specific mutations induced by (+/-)-3 alpha,4 beta-dihydroxy- 1 alpha,2 alpha-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene in the dihydrofolate reductase gene.
- DNA strand-specific repair of (+-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene adducts in the hamster dihydrofolate reductase gene.
- Malignant transformation of human fibroblast cell strain MSU-1.1 by (+-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene.
- Kinds of mutations formed when a shuttle vector containing adducts of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene replicates in human cells.
- Error-free excision of the cytotoxic,mutagenic N2-deoxyguanosine DNA adduct formed in human fibroblasts by (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.