Interactions within the mammalian DNA methyltransferase family.
BACKGROUND
In mammals, epigenetic information is established and maintained via the postreplicative methylation of cytosine residues by the DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b. Dnmt1 is required for maintenance methylation whereas Dnmt3a and Dnmt3b are responsible for de novo methylation. Contrary to Dnmt3a or Dnmt3b, the isolated C-terminal region of Dnmt1 is catalytically inactive, despite the presence of the sequence motifs typical of active DNA methyltransferases. Deletion analysis has revealed that a large part of the N-terminal domain is required for enzymatic activity.


RESULTS
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.


CONCLUSIONS
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.
Margot
Jean B
JB
Ludwig Maximilians University, Department of Biology II, Goethestr, 31, D-80336 Munich, Germany. margot@fvk-berlin.de
Ehrenhofer-Murray
Ann E
AE
Leonhardt
Heinrich
H
D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D000818:Animals; D019556:COS Cells; D020134:Catalytic Domain / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D002522:Chlorocebus aethiops; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000090205:DNA Methyltransferase 3A; D015254:DNA Modification Methylases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D051379:Mice; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D020798:Two-Hybrid System Techniques; D000097584:DNA Methyltransferase 3B
D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D015254:DNA Modification Methylases; D018076:DNA, Complementary; D010455:Peptides; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C000715535:Dnmt3a protein, mouse; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse