Binding of [3H]benzo(a)pyrene metabolites to the AKR mouse embryo cell line nuclear proteins

Nuclear proteins from AKR-2B mouse embryo cells incubated 24 hr with [3H]benzo(a)pyrene (1 microgram/ml; 10 microCi/ml) were purified to remove nucleic acids and characterized by isoelectric focusing and sodium dodecyl sulfate gel electrophoresis on polyacrylamide gels. Analysis of the nuclear proteins by isoelectric focusing revealed a distribution of protein in the pH gradient with two prominent bands of proteins, one focusing at pH 5 and the other at pH 11, both of which bound significant amounts of the carcinogen. The acid-soluble proteins from the nuclear preparation were analyzed by isoelectric focusing, and the results also revealed two peaks of protein and radioactivity at pH's of 5 and 11. Further analysis of the acid-soluble fraction on acid urea gels revealed that significant radioactivity was associated with proteins that migrated near but slower than histone H1 which may be the high-mobility group proteins 1 and 2. Radioactivity also comigrated with histones H3 and H2B. Low levels of radioactivity were associated with histone H1 and H4.