In vitro enzymatic methylation of DNA substituted by N-2-aminofluorene.

Both the initial velocity and the overall methylation of DNA substituted by aminofluorene, by a rat liver DNA(cytosine-5-)-methyltransferase, are increased as compared to native DNA. The Km and Vmax of the modified DNA for the enzyme increase as a function of the extent of modification. The carcinogen may induce a secondary structure favouring the 'walking' of the enzyme along the DNA. The hypermethylation caused by this carcinogen could have a significance in gene activity, cellular differentiation and cancer induction.