Interactions within the mammalian DNA methyltransferase family

The role played by the N-terminal domain in this regulation has been investigated using the yeast two-hybrid system. We show here the presence of an intra-molecular interaction in Dnmt1 but not in Dnmt3a or Dnmt3b. This interaction was confirmed by immunoprecipitation and was localized by deletion mapping. Furthermore, a systematic analysis of interactions among the Dnmt family members has revealed that DNMT3L interacts with the C-terminal domain of Dnmt3a and Dnmt3b.The lack of methylating ability of the isolated C-terminal domain of Dnmt1 could be explained in part by a physical interaction between N- and C-terminal domains that apparently is required for activation of the catalytic domain. Our deletion analysis suggests that the tertiary structure of Dnmt1 is important in this process rather than a particular sequence motif. Furthermore, the interaction between DNMT3L and the C-terminal domains of Dnmt3a and Dnmt3b suggests a mechanism whereby the enzymatically inactive DNMT3L brings about the methylation of its substrate by recruiting an active methylase.The mechanism of how chromatin architecture is established, maintained and modified is crucial for a thorough understanding of gene regulation and DNA replication. In higher eukaryotes DNA methylation and histone modifications appear to be the main agents responsible for the formation of active or inactive chromatin. However, what has become clear in the last few years is that the enzymes responsible for these epigenetic modifications do not act independently, but interact with one another.DNA methylation or the transfer of a methyl group to the cytosine of CpG dinucleotides is carried out by DNA methyltransferases (MTases). In eukaryotes, these enzymes are grouped into one family consisting of five members: Dnmt1, Dnmt2, Dnmt3a, Dnmt3b and Dnmt3L [1,2]. Dnmt1 is responsible for the maintenance of DNA methylation after each round of replication [3,4]. Dnmt3a and Dnmt3b are the main players involved in de novo me