SELECTIVE-INHIBITION OF CYTOSINE-DNA METHYLASES BY POLYAMINES

We have advanced the hypothesis that polyamines affect DNA methylation and thus promote the expression of developmentally controlled genes. We demonstrate that the activity of cytosine-DNA methyltransferases Hp aII, HhaI, HaeIII and SssI is inhibited by physiological concentration s of polyamines. On the other hand, activity of the adenine-DNA methyl transferase EcoRI, and restriction enzymes HpaII, HhaI, HaeIII and Eco RI, is insensitive to polyamine concentrations up to 40 mM. Our result s indicate that the effect of polyamines on cytosine-DNA methyltranfer ases is rather selective and suggest a possible mode of action in vivo .