Human DNMT2 methylates tRNA(Asp) molecules using a DNA methyltransferase-like catalytic mechanism.
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.
Biochemistry Laboratory, School of Engineering and Science, Jacobs University Bremen, 28759 Bremen, Germany.
Tomasz P
TP
Jurkowski
Madeleine
M
Meusburger
Sameer
S
Phalke
Mark
M
Helm
Wolfgang
W
Nellen
Gunter
G
Reuter
Albert
A
Jeltsch
D000595:Amino Acid Sequence; D000818:Animals; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004023:Dictyostelium / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012349:RNA, Transfer, Asp / Q000378:metabolism*; D016415:Sequence Alignment; D012359:tRNA Methyltransferases / Q000737:chemistry / Q000378:metabolism
D012349:RNA, Transfer, Asp; D012359:tRNA Methyltransferases; D004248:DNA (Cytosine-5-)-Methyltransferases; C112218:TRDMT1 protein, human