DNA methylation plays a critical role in controlling states of gene activity in 
most eukaryotic organisms, and it is essential for proper growth and 
development. Patterns of methylation are established by de novo 
methyltransferases and maintained by maintenance methyltransferase activities. 
The Dnmt3 family of de novo DNA methyltransferases has recently been 
characterized in animals. Here we describe DNA methyltransferase genes from both 
Arabidopsis and maize that show a high level of sequence similarity to Dnmt3, 
suggesting that they encode plant de novo methyltransferases. Relative to all 
known eukaryotic methyltransferases, these plant proteins contain a novel 
arrangement of the motifs required for DNA methyltransferase catalytic activity. 
The N termini of these methyltransferases contain a series of 
ubiquitin-associated (UBA) domains. UBA domains are found in several ubiquitin 
pathway proteins and in DNA repair enzymes such as Rad23, and they may be 
involved in ubiquitin binding. The presence of UBA domains provides a possible 
link between DNA methylation and ubiquitin/proteasome pathways.