Comparative analysis of DNA methylation patterns in transgenic Drosophila overexpressing mouse DNA methyltransferases.
DNA methyltransferases (Dnmts) mediate the epigenetic modification of eukaryotic genomes. Mammalian DNA methylation patterns are established and maintained by co-operative interactions among the Dnmt proteins Dnmt1, Dnmt3a and Dnmt3b. Owing to their simultaneous presence in mammalian cells, the activities of individual Dnmt have not yet been determined. This includes a fourth putative Dnmt, namely Dnmt2, which has failed to reveal any activity in previous assays. We have now established transgenic Drosophila strains that allow for individual overexpression of all known mouse Dnmts. Quantitative analysis of genomic cytosine methylation levels demonstrated a robust Dnmt activity for the de novo methyltransferases Dnmt3a and Dnmt3b. In addition, we also detected a weak but significant activity for Dnmt2. Subsequent methylation tract analysis by genomic bisulphite sequencing revealed that Dnmt3 enzymes preferentially methylated CpG dinucleotides in a processive manner, whereas Dnmt2 methylated isolated cytosine residues in a non-CpG dinucleotide context. Our results allow a direct comparison of the activities of mammalian Dnmts and suggest a significant functional specialization of these enzymes.
Mund
Cora
C
Research Group Epigenetics, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
Musch
Tanja
T
Strödicke
Martin
M
Assmann
Birte
B
Li
En
E
Lyko
Frank
F
D000818:Animals; D030801:Animals, Genetically Modified; D002875:Chromosomes / Q000201:enzymology; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D015870:Gene Expression; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism; D000097584:DNA Methyltransferase 3B
D004248:DNA (Cytosine-5-)-Methyltransferases; D029721:Drosophila Proteins; D020033:Protein Isoforms; D000097584:DNA Methyltransferase 3B; C491786:Dnmt2 protein, mouse; C491784:Mt2 protein, Drosophila