Structure, conformations, and repair of DNA adducts from dibenzo[a, l]pyrene: 32P-postlabeling and fluorescence studies.
The nature of stable DNA adducts derived from the very potent carcinogen dibenzo[a,l]pyrene (DB[a,l]P) in the presence of rat liver microsomes in vitro and in mouse skin in vivo has been studied using 32P-postlabeling and laser-based fluorescence techniques. Analysis of DB[a,l]P-DNA adducts via 32P-postlabeling has been obtained by comparison of the adduct patterns to those obtained from reactions of synthetic (+/-)-anti-, (+)-anti-, (-)-anti-, and (+/-)-syn-DB[a,l]P-11,12-diol 13,14-epoxide (DB[a,l]PDE) with single nucleotides and calf thymus DNA. anti-DB[a,l]PDE-dA adducts derived from the (-)-enantiomer are the major adducts formed in calf thymus DNA and in mouse skin DNA. The ratio of deoxyadenosine to deoxyguanosine modification is approximately 2:1 in mouse skin exposed to DB[a,l]P; activation by rat liver microsomes leads to a similar profile of adducts but with two additional spots. The conformations of DB[a,l]P adducts in native DNA, as well as the possibility of conformation-dependent repair, have been explored by low-temperature fluorescence spectroscopy. These studies have been performed using polynucleotides and calf thymus DNA reacted in vitro with DB[a,l]PDE and native DNA from mouse epidermis exposed to DB[a, l]P. The results show that adducts are heterogeneous, possess different structures, and adopt different conformations. External, external but base-stacked and intercalated adduct conformations are observed in calf thymus DNA and in mouse skin DNA samples. Differences in adduct repair rates are also revealed; namely, the analysis of mouse skin DNA samples obtained at 24 and 48 h after exposure to DB[a,l]P clearly shows that external adducts are repaired more efficiently than intercalated adducts. These results, taken together with those for B[a]P-DNA adducts [Suh et al. (1995) Carcinogenesis 16, 2561-2569], indicate that the repair of DNA damage resulting from PAH diol epoxides is conformation-dependent.
Jankowiak
R
R
Ames Laboratory-USDOE and Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA. jankowiak@ameslab.gov
Ariese
F
F
Hewer
A
A
Luch
A
A
Zamzow
D
D
Hughes
N C
NC
Phillips
D
D
Seidel
A
A
Platt
K L
KL
Oesch
F
F
Small
G J
GJ
D000818:Animals; D001580:Benzopyrenes / Q000737:chemistry / Q000378:metabolism*; D002273:Carcinogens / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D018736:DNA Adducts / Q000737:chemistry*; D004260:DNA Repair; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D009690:Nucleic Acid Conformation; D051381:Rats; D012867:Skin / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D001580:Benzopyrenes; D002273:Carcinogens; D018736:DNA Adducts; C041517:dibenzo(a,l)pyrene