DNA methylation in eukaryotes

Abstract

In prokaryotes, DNA methylation protects the bacteriaÕs DNA against degradation by restriction enzymes and corrects error in DNA replication by means of the mismatch repair system. In 1964, the first DNA methyltransferase was identified in E. coli. The avaiability of sequence-specific restriction enzymes and methyltransferases led to a major breakthrough in the field of molecular biology. In eukoryotes, DNA methylation appears to have a different role. It has been implicated in the control of several cellular processes, including differentiation, gene regulation and embryonic development. A series of discoveries over the past few years has generated new interest in DNA methylation. It has been found that in mice in particular DNA methyltransferase is essential for normal embryonic development. Cytosine methylation may also contribute to C-T transition mutations, accounting for about one-third of all somatic and germline mutations in humans.