Preferential binding of aflatoxin B1 to the transcriptionally active regions of rat liver nucleolar chromatin in vivo and in vitro.

The literature on various isolated carcinogen-DNA adducts indicates clearly that the binding of chemical carcinogens to DNA is highly specific. Since DNA in eukaryotic cells is complexed with chromosomal proteins and organized into transcriptionally active and inactive chromatin, chemical carcinogens also might show binding specificities at the chromatin level. Using Escherichia coli RNA polymerase and the endogenous engaged RNA polymerase I as specific probes to monitor respectively the physiologically inactive and active nucleolar chromatin template function, this paper reports that aflatoxin B1, after metabolic activation either in vivo or in vitro, binds preferentially to the physiologically active regions of rat liver nucleolar chromatin, and that this binding specificity is largely lost after the removal of chromosomal proteins from the nucleoli.