title: Dnmt2 is not required for de novo and maintenance methylation of viral DNA in embryonic stem cells.
abstract: We have shown previously that de novo methylation activities persist in mouse embryonic stem (ES) cells homozygous for a null mutation of Dnmt1 that encodes the major DNA cytosine methyltransferase. In this study, we have cloned a putative mammalian DNA methyltransferase gene, termed Dnmt2 , that is homologous to pmt1 of fission yeast. Different from pmt1 in which the catalytic Pro-Pro-Cys (PPC) motif is 'mutated' to Pro-Ser-Cys, Dnmt2 contains all the conserved methyltransferase motifs, thus likely encoding a functional cytosine methyltransferase. However, baculovirus-expressed Dnmt2 protein failed to methylate DNA in vitro . To investigate whether Dnmt2 functions as a DNA methyltransferase in vivo , we inactivated the Dnmt2 gene by targeted deletion of the putative catalytic PPC motif in ES cells. We showed that endogenous virus was fully methylated in Dnmt2 -deficient mutant ES cells. Furthermore, newly integrated retrovirus DNA was methylated de novo in infected mutant ES cells as efficiently as in wild-type cells. These results indicate that Dnmt2 is not essential for global de novo or maintenance methylation of DNA in ES cells.
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Department of Medicine,Harvard Medical School, 149, 13th Street, Charlestown, MA 02129, USA.
authors.forename: M
authors.initials: M
authors.lastname: Okano
authors.forename: S
authors.initials: S
authors.lastname: Xie
authors.forename: E
authors.initials: E
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D003001:Cloning, Molecular; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004279:DNA, Viral / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000235:genetics; D011533:Proviruses / Q000235:genetics; D012568:Schizosaccharomyces; D013234:Stem Cells
chemical_list: D004279:DNA, Viral; C491786:Dnmt2 protein, mouse; D004248:DNA (Cytosine-5-)-Methyltransferases; C112218:TRDMT1 protein, human