This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lloyd, D. R. Articles by Hanawalt, P. C. Search for Related Content PubMed PubMed Citation Articles by Lloyd, D. R. Articles by Hanawalt, P. C.

p53 Controls Global Nucleotide Excision Repair of Low Levels of Structurally Diverse Benzo(g)chrysene-DNA Adducts in Human Fibroblasts¹

Department of Biological Sciences, Stanford University, Stanford, California 94305-5020 [P. C. H.], and Research School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, United Kingdom [D. R. L.]

Benzo(g)chrysene is a widespread environmental contaminant and potent carcinogen. We have measured the formation and nucleotide excision repair of covalent DNA adducts formed by the DNA-reactive metabolite of this compound in human fibroblasts, in which expression of the p53 tumor suppressor gene could be controlled by a tetracycline-inducible promoter. Cells were exposed for 1 h to 0.01, 0.1, or 1.2 µM (±)-anti-benzo(g)chrysene diol-epoxide, and DNA adducts were assessed at various post-treatment times by subjecting isolated DNA to ³²P-postlabeling analysis. Four major DNA adducts were detected, corresponding to the reaction of either the (+)- or (-)-anti-benzo(g)chrysene diol-epoxide stereoisomer with adenine or guanine. Treatment with 1.2 µM resulted in a level of 1100 total adducts/10⁸ nucleotides for both p53-proficient and -deficient cells; removal of adducts was not observed in either case. In cells treated with 0.1 µM, the maximum level of total adducts at 24 h was 150/10⁸ nucleotides in p53-proficient cells and 210 adducts/10⁸ nucleotides in p53-deficient cells. A concentration of 0.01 µM resulted in a maximum of 20 adducts/10⁸ nucleotides in p53-proficient cells at 4 h, but 40 adducts/10⁸ nucleotides persisted in p53-deficient cells at 24 h. Whereas there were clear differences in the time course of adduct levels in p53-proficient compared with p53-deficient cells treated with 0.1 µM or 0.01 µM, these levels did not decrease extensively over 3 days. This is likely because of the stabilization of the diol-epoxide in cells, and consequent exposure and formation of adducts for many hours after the initial treatment. Furthermore, despite minor quantitative differences, all 4 of the adducts behaved similarly with respect to the effect of p53 expression on their removal. p53 appears to minimize the appearance of benzo(g)chrysene adducts in human cells by up-regulating global nucleotide excision repair and reducing the maximum adduct levels achieved. The fact that this p53-dependent effect is noted at levels of DNA adducts that are commonly found in human tissues (i.e., <100 adducts/10⁸ nucleotides) because of environmental factors such as smoking is particularly significant with respect to human carcinogenesis related to environmental exposure.

This article has been cited by other articles:

				S. Bhana, A. Hewer, D. H. Phillips, and D. R. Lloyd p53-dependent global nucleotide excision repair of cisplatin-induced intrastrand cross links in human cells Mutagenesis, March 1, 2008; 23(2): 131 - 136. [Abstract] [Full Text] [PDF]

				S. Bhana and D. R. Lloyd The role of p53 in DNA damage-mediated cytotoxicity overrides its ability to regulate nucleotide excision repair in human fibroblasts Mutagenesis, January 1, 2008; 23(1): 43 - 50. [Abstract] [Full Text] [PDF]

				D. Medina and F. S. Kittrell p53 Function Is Required for Hormone-Mediated Protection of Mouse Mammary Tumorigenesis Cancer Res., October 1, 2003; 63(19): 6140 - 6143. [Abstract] [Full Text] [PDF]