Stimulation of de novo methylation following limited proteolysis of mouse ascites DNA methylase.

The ability of mouse Krebs II ascites cell DNA methylase to add methyl groups to native, unmethylated DNA (de novo activity) is stimulated by limited proteolysis. The affinity of the enzyme for DNA is not altered by this treatment but the rate of reaction is increased so that 40% or more of methylatable sites are methylated within 4.5 h. The activation is associated with a decrease in size of the enzyme to 6.2 S.