Binding of benzo(a)pyrene to rat liver nuclear matrix

Binding of benzo(a)pyrene (B(a)P) to nuclei isolated from rat liver was investigated. After incubation with ¹⁴C-B(a)P, the nuclei were subfractionated into an envelope fraction, two chromatin fractions and a matrix fraction. About 50% of the B(a)P that entered the nuclei was associated with the matrix fraction. Covalently bound B(a)P in the matrix fraction also exceeded that in the chromatin fractions. The radioactivity of ¹⁴C-B(a)P attained by the matrix DNA was 3–5 times higher than that attained by the chromatin DNAs. These findings suggest that the nuclear matrix is a major intranuclear binding site of B(a)P.