Selective modification of nuclear proteins by polycyclic aromatic hydrocarbons and by benzo[a]pyrene diol epoxides

Abstract
Metabolites of benzo[a]pyrene (B[a]P) have been shown to modify chromosomal proteins with great specificity. Using the (+) and (−) enantiomers of anti -B[a]P diol epoxide to label isolated nuclei we found a remarkable difference in the capacity of these two compounds to modify histones H2A and H3. The (+) enantiomer modified histones H2A and H3, while the (−) enantiomer, which was shown to modify mainly histone H2A, had a much lower affinity for histone H3. We have also examined the selective modification of chromosomal proteins by different polycyclic aromatic hydrocarbons and it was observed that 7,12-dimethylbenz[a]-anthracene (DMBA), 3-methylcholanthrene (3-MC) and B[a]P showed qualitative similarities in terms of their protein binding. This suggests that stereospecific interactions leading to binding of reactive metabolites of DMBA, B[a]P and 3-MC to chromosomal proteins share common features.

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