Binding of the carcinogens 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene and its acetate ester to DNA in vitro

Binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene to calf thymus DNA was negligible (1.2 μmole hydrocarbon/mole DNA-P) in the absence of microsomal enzymes whereas in the presence of liver microsomes from unpretreated rats or from rats pretreated with 3-methylcholanthrene binding was greatly enhanced (11.6 and 16.2 μmole hydrocarbon/mole DNA-P respectively). In contrast, the acetate ester of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene readily bound to DNA non-enzymatically (9.1 μmole hydrocarbon/mole DNA-P). In the presence of a 3′-phosphoadenosine-5′-phosphosulfate (PAPS) generating system, the binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene was independent of sulfate ion. ATP enhanced non-enzymatic binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene to DNA whereas CTP, β,γ-methylene-ATP, and ADP were much less effective suggesting a certain specificity for adenosine in addition to a high energy triphosphate for high binding. These observations suggest that 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene may be converted to a phosphate ester which, like 5-fluoro-7-acetoxymethyl-12-methylbenz(a)anthracene, readily binds to DNA.