Although their amino acid sequences and structure closely resemble DNA 
methyltransferases, Dnmt2 proteins were recently shown by Goll and colleagues to 
function as RNA methyltransferases transferring a methyl group to the C5 
position of C38 in tRNA(Asp). We observe that human DNMT2 methylates tRNA 
isolated from Dnmt2 knock-out Drosophila melanogaster and Dictyostelium 
discoideum. RNA extracted from wild type D. melanogaster was methylated to a 
lower degree, but in the case of Dictyostelium, there was no difference in the 
methylation of RNA isolated from wild-type and Dnmt2 knock-out strains. 
Methylation of in vitro transcribed tRNA(Asp) confirms it to be a target of 
DNMT2. Using site directed mutagenesis, we show here that the enzyme has a DNA 
methyltransferase-like mechanism, because similar residues from motifs IV, VI, 
and VIII are involved in catalysis as identified in DNA methyltransferases. In 
addition, exchange of C292, which is located in a CFT motif conserved among 
Dnmt2 proteins, strongly reduced the catalytic activity of DNMT2. Dnmt2 
represents the first example of an RNA methyltransferase using a DNA 
methyltransferase type of mechanism.