Mammalian DNA methyltransferases prefer poly(dI-dC) as substrate.
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TL;DR
The apparent slower rate of de novo methylation of poly(dI-dC) as compared to the hemimethylated derivative is due to substrate inhibition, unique to the unmethylated polymer, as the rates ofde novo and maintenance methylation are identical at low substrate concentrations.
Abstract
The synthetic duplex DNA, poly(dI-dC).poly(dI-dC), is methylated in vitro by human or murine DNA methyltransferases at 20-100 times the rate of other nonmethylated DNAs. Preparation of the hemimethylated derivative, poly(dI-dMeC).poly(dI-dC), of this polymer increases its effectiveness as a substrate by 2-fold, making it 4-10 times more effective as a substrate for mammalian DNA methyltransferases than any other hemimethylated DNA so far reported. However, the apparent slower rate of de novo methylation of poly(dI-dC).poly(dI-dC) as compared to the hemimethylated derivative is due to substrate inhibition, unique to the unmethylated polymer, as the rates of de novo and maintenance methylation are identical at low substrate concentrations.